"Split" as the name for a 100ml bottle of liquor.

I live in North Florida in a neighborhood that's a little rough around the edges but it has character and I like my neighbors.

For good or ill the liquor store at the end of the street is a sort of gathering place in the evenings and often there are a few people surreptitiously sipping from 100ml bottles of liquor.   These bottles are one size up from the single serving ones sold on airplanes, and one down from the half-pint bottles.

I was informed that this size is called a "split".   On hearing this I wondered "what's being split? Or is its small size the result of a larger size having been split?   Or is it a corrupted form of another word?"

I've asked around at liquor stores in town and the term is in widespread use here.   Googling and posting to spirits appreciation forums has given me no results and no one has claimed to have heard the term before.

I did get a response from the editor at Modern Drunkard magazine and he told me the term has been used in reference to a half sized bottle of champagne since at least the late 1800s and perhaps it carried over from that to these diminutive bottles.

I had decided that it must just be a local term when out of the blue one of my pen pals got back to me and told me he had been told by a store clerk in NYC that the bottles of the 100ml size were called splits.

So now I'm back to being unsure as to the origin of this term.   Perhaps it is local and the clerk up there just happened to be from North Florida.   Maybe it's an old word or a brand new one (though I doubt the latter as I'm a bit old and so are the folks at the end of the street.)

Do any of you all have any insight into this term?   Is it Southern, is it rural, why is figuring this out so deeply stuck in my craw?

Any help would be appreciated.   It's becoming one of those two o'clock thoughts that keep me from sleeping.

Thank you.