I am forwarding a question from a friend of mine, for which I do not have a clear answer:
Dear Madhav,
I thought you might have a quick answer to this question. When mentioning gotras, one sees "Visvāmitra gotra", but also "Ātreyasa gotra", and "Kāsyapasa gotra".
Since the ṛṣis in the two latter cases are Atri and Kasyapa, it would appear that the corresponding gotras should be "Ātreya" and "Kāsyapa", without the "sa" suffix. (Indeed, one also sees "Ātreya gotra", and "Kāsyapa gotra".)
Is it the case that the correct terms are "Ātreya sagotra", and "Kāsyapa sagotra", and the conventional usage is simply an incorrect parsing? However, this would require "Visvāmitra sagotra", which one does not see.
Or is there something more to it than that?
Why would someone be referred to as Viśvāmitra-gotra, but others as Ātreya-sagotra or Kāśyapa-sagotra? I will appreciate a clarification.