This is a facts board, and many of the statements in the post above are not clearly defensible as facts. Most of the following is probably off-topic, so please take any discussion related to those aspects elsewhere. (I have a signature below if you want to discuss it offline).
I do not know if the etymology of somaiah given above is correct or not, but it is correct that without further information both moon and the ancient drink are equally likely elements in the name.
Part of the problem is that the aiah is not a Sanskrit form. somArya exists as a Sanskrit name where the Arya element (same as in the root of the word Aryan) means honourable from a root meaning to go straight or rise (This root R has cognates all over and Arya itself has the cognate Ehre in German and Erin in Irish). The r in the word Arya has often been softened into non-existence in Neo-Indo-Aryan languages. A far more common word and epithet in Vedic is somArha, where arha means deserving (cognates exist in Greek).
The word soma itself is from a root meaning to press and simply means juice. There was a popular drink which was so important that it itself was deified, and was considered the drink of the gods! We do not know, however, what this drink was: we know for sure that even in the 19th century, a particular plant was called soma in Hindu religious contexts and another haoma (the cognate) in Persian. Neither of these two are likely to have been the original, and there is literary evidence that the identity of the plant changed because of difficulty in obtaining it. In any case, it is only one of the theories that it was a hallucinogenic mushroom: I personally like the theory that is some kind of ephedra, though I am not a historian.
The statements that most Indians come from Aryan tribes is less defensible. `Aryan' is properly speaking a linguistic classification: and all indications are that they originated from a group of related languages, possibly over a largish area of cultural contact centered somewhere in Central Asia, about seven thousand years back. Indian languages clearly have roots in this Aryan (or, the preferred term, Indoeuropean), Dravidian, Austrasiatic, and Tibeto-Burman families, and it is difficult to claim that most Indians are Aryans. Genetically, very little of the makeup of most of India changed that recently; though one can find clear genetic correlates of the linguistic family showing the accompanying diffusion of peoples. Culturally, there are very strong clines diving the north-west from the south-east which might have some bearing on the problem.
The story of deification of Indra has no evidence for it (but, to be sure, none against it either). The name indra however is related to the root ind meaning to drop, and indra is the rain god as well. Much of the indra mythology can also be thought of as the life-giving rains breaking through the clouds.
When one is talking about indra, apollo and thor having the same roots, it is not the linguistic roots! What seems to have happened is that the mythology had multiple concepts which were close (i.e. distinctions were not large enough to have been maintained for seven millenia or quarter of a thousand generations), and at different times and different places, one of the concepts, and sometimes one aspect of it, has grown to dominance and taken over the related roles. We thus find non-cognate words for cognate concepts in the pantheon, and vice-versa.