A full glass; in all likelihood from its convexity or bump at the top: some derive it from a full glass formerly drunk to the health of the pope—au bon pere.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Bummed * BumpingNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes