Although GOD is known by many names but the most prominent name given by the Vedas is “AUM” or “AOM” pronounced as ‘OM’. The meaning of this three-letter word as explained by the Great Swami Dayananda Saraswati –

‘A’ stands for Virat, Agni and Vishwa etc.

‘U’ or ‘O’ stands for Hiranyagarbha, Vayu and Tajas etc.

‘M’ stands for Ishwara, Aditya and Prajna etc.

An etymological exposition of AUM

1. Virat signifies God, because He illuminates this multiform universe.
2. Agni signifies Gati and Worship. Gati means to know, to move or go, and to realize. Agni connotes God because He is all – knowledgeable, Omniscient and worthy of adoration, fit subject to be known, sought after and realized.
3. Vishwa means God, because the entire world and worldly objects dwell in Him and He resides in all of them.
4. Hiranyagarbha (Hiranya - light and garbha - source) means one who is the source and support of all light and luminous bodies such as the Sun. This is also substantiated by Yajur Veda, which says: - " In the beginning was Hiranyagarbha - the One Lord of the creation. He sustains the sun and the earth. We adore Him - the all Blissful Being." YAJUR VEDA 13: 4. Hiranyagarbha also means that He sustains all.
5. Vayu means one who is the life and support of the Universe, the cause of its dissolution, mightier than the mightiest.
6. Tajes is one who is resplendent and gives light to the Sun and other luminous bodies.
7. Ishwar is one whose knowledge and power are infinite.
8. Aditya is one who never dies or decays – is Immortal.
9. Prajna is one whose knowledge is perfect - who is omniscient.

The above is taken from Ch1 of Maharishi Dayanand’s “Satyarth Prakash”. Now let’s try and summarise the exposition of AUM with respect to the Upanishads:

Mundakopnishad says that Pranav (AUM) acts like a bow in Upasana and the arrow is the Atma. The objective is Braham.

Mandukopnishad says AUM is a small word. The whole World is the exposition of this little word. Not only the present world but the past and future worlds are also the exposition of AUM. All that is beyond past, present and future is also AUM. Whatever is the Kaal of Kaal is also AUM.

1. As Atma is in the body, likewise the Jagrit (awake) Sthan of Brahman in Prakriti is known as the Vaishvanar (which organises or arranges) Sharir is called the first Matra ‘A’ of AUM. ‘A’ is also the first of all the letters. Apta knows that the Upasana of first letter fulfils all legitimate desires worship the first Matra.
2. As Atma is in the body, likewise the Swapn (dream) Sthan of Brahman in Prakriti is known as the Tajes (resplendent) Sharir. ‘U’ being in middle is said to have relationship with both ‘A’ & ‘M’. It is Tajes because it is in the situation of being respected by both ‘A’ & ‘M’. Brahma Jnani knowing this has all his/her future generations learned of Veda. This implies that even Grihasta can become Brahma Jnani and Jivan Mukta i.e. Humans can achieve Moksha irrespective of belonging to any of the 4 Varna Ashrams (few people have incorrectly preached that a person can only achieve Moksha through the 4^th Ashram by being a Sanyasi).
3. As Atma is in the body, likewise the Shusupta (dream) Sthan of Brahman in Prakriti is known as Prajya (All Knowledge) Sharir and is called Makaar. God is said to be in Shusupta (Jnana Swaroop – bliss) state during Pralay. In Shusupta state Jagrit and Swapn states end. Whoever knows Parmatma as the third Matra ‘M’ knows the world in its true state and becomes free after leaving the body.

Now that we have attempted to give the exposition of AUM from three Upanishads, let’s attempt to give a summary from Gopath Brahman.

AUM is known as the eldest son of God (it has been explained with the medium of a story in the Brahman) because it is the first letter of the spoken language in the Shristhi. AUM is to be added in front of every mantra before chanting the whole mantra.

1. The first Matra of AUM is Rakta Varna (Blood or Red colour). This means ‘A’ is for Prakash (knowledge) or Braham Sthan.
2. The second Matra of AUM is Kala Varna (Black or absence of colour). This means ‘U’ or ‘O’ is for omnipresence and sustainer of world. It is called Vishnu Pad.
3. The third Matra of AUM is Peela Varna (yellow colour). This represents the Braham Muhurta of Aishan Pad (place of everybody’s God).
4. The fourth half Matra is of bright Villormani colour. This depicts the nameless God pad. It is all Devtas and refulgent and roams in Akash.

Gopath Brahman has explained it more deeply by giving the relationship of AUM with the creation aspect, giving questions and answers etc. AUM has also been explained in All Brahman Granths, Samhitas, Darshan Granths and Manu Smriti etc.

Now before we proceed further, lets try reasoning the existence of GOD.  

When we minutely think about the objects in the world we realize that there are many objects in the world. All actions in those objects are bounded by some law e.g.. a child is born and grows for some time and then he starts on the path of decline and one day dies. The law we found from this example is that any thing that is born changes state and dies in the end.

Now that we have seen that the objects that change its state is made or born; lets see if this world is without birth or not.

Since the world is changing we can say that it has been created or born. Many people might say that they do not see the world change; only the things in it change. But if you think deeply you will realize that anything whose aspects changes is also viable to change. Since world is the collective name of visible & invisible things and all those things change; we can say that the world also changes. Hence, it is born and is destructible.

Now that its been reasoned out that the world is created or is born; a question arises that creation is of two types - Habitual (Swabhavik) and Accidental or Occasional (Naimittik). When we go to any jungle or hill or place and see lots of trees and plants we say that these trees have grown naturally or habitually; but if we go to a garden and see rows of flowers and vegetables we say that these have been planted by some knowledgeable person. Thus we can say that there is a law or rule of sowing is working in this garden. It is a known fact that there are rules and laws of the world. Hence it can be said that the world is created or made. 

Many people say that mixing of red and blue colors generate black, likewise Soul is created from Prakriti Material. Deep thinking and reasoning intellect people know that one color is stopping the effect of the other and both of them float away from the reality and generate black.

Now that we have reasoned out that the world is ever changing and hence it is born or created due to the rules and law, we can also say that it has an intelligent creator. This intelligent creator is called God.

Another example we can try is to attempt to reason out the power or energy behind a Nebula. A Nebula in short can be described as a phenomenon of the first stage of a stars cycle. It happens from the gravitational collapse of diffused gases in an interstellar medium. These gases and the cosmic dust are created or made from Prakriti.

Gases diffuse when the adhaar (base or support) for them is removed e.g. the adhaar of hydrogen gas in a gas bottle is the bottle itself. Once this adhaar is removed the hydrogen gas in the bottle is free to mix with other atmospheric gases. Thus, becoming practically useless for the purpose it was originally filled into the bottle. Similarly, human is the adhaar or efficient cause of the gas bottle (making or creating the bottle and filling it with the hydrogen gas). What we gather from this is that the human has made the bottle from the materials already existing and filled in the hydrogen gas which was also existing. Hence, the efficient cause (human in this case) has provided the adhaar for the gas to be bottled. Similarly, there has to be a power or energy as the source of adhaar for the gravitation and its collapse. An energy or power source should be present as the efficient cause for the activity of Nebula. This efficient cause cannot be soul as it is limited in its capability. This efficient cause is called God and is known by the name AUM (pronounced as OM) as per the knowledge given by the Vedas.

Below is the English translation of few Q & A from Maharishi Dayanand's Satyarth Prakash:

Q: How can you prove his existence?

A: By the evidences of direct cognition, Inference, Testimony and History.

Q: But there can be no evidence of direct cognition, with regard to God?

A: "The knowledge which is the result of the direct contact of the five senses - optic, auditory, olfactory, gustatory and tactile - and of the mind, with light, sound , smell, taste and touch; with feelings of pleasure and pain truth and untruth is called direct cognition. But this knowledge must be free from error and doubt". Niyaya Shastra 1,4.

On reflection it will be clear that it is only attributes that can be known through the senses and the mind, not substances, in which those qualities inhere. As for example, we are cognizant of a solid substance when it gives rise to the sensations of touch, smell, etc., by coming in contact without four senses, such as the tactile sense, and the senses with the mind, and the latter with the soul; similarly we are cognizant of the existence of God by observing such qualities as design and intelligence in this world.

Besides, instantly the soul directs the mind and the latter directs the senses to the pursuit of a certain object either good - such as acts that promote public welfare - or bad such as theft, they all incline to the desired object and at that very moment, feelings of fear, shame , and distrust arise in the self consciousness if the action be sinful, and those of fearlessness, courage, and satisfaction of felicity, if it be good; these feelings are prompted not by the human soul, but by the Divine Spirit.

Lastly when the soul, freed from all impurities, devotes itself to the contemplation and realization of God through Yoga, it becomes cognizant of both - itself and the Divine Spirit. When we can be directly cognizant of the existence of God how can there be any doubt. His existence by inference and other evidence, because the cause is inferred from its effects.

Now that we have reasoned out HIS existence, lets try to discuss about his form:

Even though He is said to be a 4 handed person or Seated on Throne with his son sitting on his right or an Elephant head person and many more forms by people of different beliefs, but in real God is formless. If God possesses a form He could never be free from hunger and thirst, heat and cold, disease, imperfections and injuries. This proves, therefore that God is formless. If He were to possess a body, another person would be required to make the different organs of His body, such as eyes, ears and the like, for He, who is the product of the combination of the different – parts, must have an intelligent form maker. Here if it be urged that God Himself made His body simply by willing it, this too goes to prove that He was formless before He made his body. It is clear, therefore, that God is never embodied. Being without a body He is able to make the visible universe out of invisible causes.

Q. How many Gods are there in Vedas?

A. There is only one God and not many. The multitudes of names like Indra signify not different divine beings but different aspects of one Absolute existence.

  “ Many people are led to the idea that the Vedas inculcate the worship of innumerable Gods and Goddesses called Devatas. This word Devata is the most fruitful source of error.”  -Pundit Gurudatta Vidyarthi (The Terminology of Vedas)

  What substances then, are the Devatas? They are all that can form the subject of human knowledge. All human knowledge is limited by two conditions, i.e., time and space. Our knowledge of causation is mainly that of succession of events. And succession is nothing but an order in time. Secondly, our knowledge must be knowledge of something, and that something must be somewhere. It must have a locality of its existence and occurrence. Thus far, the circumstances of our knowledge, time and locality. Now to the essentials of knowledge. The most exhaustive division of human knowledge is between objective and subjective. Objective knowledge is the knowledge of all that passes without the human body. It is the knowledge of the phenomena of the external universe. In speaking of the subjective knowledge, there is firstly the ego, the human spirit, and the conscious entity; secondly, the internal phenomena of which the human spirit is conscious. These are again divided into “deliberate activities” and “vital activities’, and it is concluded that, since our prior analysis of the knowable leads to six things, time, locality, force, human spirit, deliberate activities and vital activities, these are fit to be called Devatas. The author of NIRUKTA (the greatest authority on Vedic interpretation) has also accounted Vedic Devatas as these six things and no other.

Q. If GOD was the three 'O" as per our Vedic scriptures (Omniscient Omnipresent Omnipotent) then why do we refer GOD as HE and not SHE or HOMO or both?

A. Since God is Omnipresent no form can be associated with him; hence no gender. Since we live in a patriarchal society a lot of reference is taken as He. In Vedas God is represented as a He, She and both. Being the protector, God is referred as a He as performing the fatherly function. Being the first efficient cause or the creator God is referred as both He and She as the seeds of Father and Mother (+ve & -ve tattavas) are required for creation. Similarly, Kalagni (cause of dissolution) is the female aspect along with the Bhumi; Indragni (electricity). Matrishwa (Powerful like wind), Indra (full of lustre), Virat (illuminator of the multiform universe) etc. are the Male aspect of the almighty. Hiranyagarbha (who keeps prakriti in womb during dissolution, also means source and support of all light and luminous bodies), Prajna (whose knowledge is perfect) can be represented as both genders. Prajna can also be represented as devoid of both Genders. Now the Nij naam of God i.e. OM is neither Male nor Female. Devas and Devis are also male and female gender respectively.

Q. We can easily refer mother nature or father time as these are considered as matter, but when we refer GOD, why is the title of HE is referred?

A. As said above Patriarchal society makes the male gender prominent. Vedic teachings do not discriminate between Male and Female (i.e. does not distinguish one gender greater than the other). However, there are certain duties which prioritise the Gender e.g. In a Grihast system, beautifying a home is prioritized to the female of the house while physically demanding work of the household is prioritized to the male. I know few females are far superior in physique and strength then most males but that is not a common occurrence. Physiology studies also explain that males have more animal strength than females. In Darshan (Philosophy) Shastras Sun (with its brightness and lustre) is referred as male while Prithivi (sharan providing and loving) is represented as female.

Father is seen as the provider and protector; hence God is mostly represented as He. There is no hard and fast rule why you can not represent God with other Gender/s.

Ish Upanishad