Green’s Dictionary of Slang

a bottle.

1895		E. Townsend Chimmie Fadden Explains 56: I wouldn’t tink I was earnin me wages if it wasn’t for Mr. Paul sayin what was de matter wid me openin a small bot for him [...] pretty often.
1902		Ade Forty Modern Fables 221: They opened two or three Cold Bots and ate a few hillocks of Cottage Cheese, Souse.
1910		O. Johnson Varmint 295: How many bots did you bring?
1913		H.A. Franck Zone Policeman 88 161: Feb. 4/2 bots beer.
1954		Wodehouse Jeeves and the Feudal Spirit 39: The kippers and the bot had arrived by now.
1961		K. Amis letter 14 Aug. in Leader (2000) 594: Brandy 6/- a bot.