Morning kaya, I assume you have read the discussion between myself and crofter. The point we differed on was that I believe the original spelling of the word came from the god Brahma and all the dictionaries I checked had Brahminism as the variant spelling, and there was no mention of alt: spelling in the clue.
Crofter, however, didn't like the fact that there was no instruction to reverse 'popular one' to read a ni, since 'a' may denote one as well. It's a small point, and I did submit both versions.
PS: I've just noticed in CED that Brahmin is the older spelling of the word, although, before it is mentioned, there are definitions for Brahma(1), Brahma(2),Brahman and Brahmana
It isn't really that serious, merely another point of view, however the day that the answer is given, I promise to have two large glasses of Bunnahabhain Islay Malt , and if my answer is wrong I'll only have one. Surely a true act of contrition for a Scotsman. Cheers.