It is an obscure word JLM, according to Reader’s Digest (and I agree with Reader’s Digest). Whenever I am waiting at the doctor, dentist, hospital etc., I always go for Reader’s Digest and look up the Word Power section. Normally I get 18 or 19 right out of 20 (I suppose that is why I like the section).
Anyway, this one issue said let us see how good you are at obscure words. There they had mentioned ‘berm’ (they had also mentioned words like ‘rodomontade’, or ‘lagniappe’, but I knew those). Anyway, normally I get 18 or 19 out of 20 correct, that day I got 10 correct.
So yes it is an obscure word, mostly those who are involved in that trade or profession would know about it.
Incidentally, my word processor does not recognize the word ‘berm’ (probably yours doesn’t recognize it as well, try it). So it is an obscure word.