In message , Ken Fortenberry
writes
Snit = 3ozs of beer.

Yeah, I know what a snit is, I just had one this morning
and I get one every time I order a Bloody Mary in Minnesota.
..

What I want to know is, how did a little glass of beer come
to be known as a snit ? I mean the definition you posted,
which is obviously correct, is not in any of my dictionaries
of American English. And my OED is at home.

"Origin unknown" is all I can find.

--
Bill Grey