Green’s Dictionary of Slang

slopped adj.

drunk.

1907		J. London Road 114: The Erie County Pen was the only place where a man could get ‘slopped’ and not be arrested.
1925		Dos Passos Manhattan Transfer 47: Honest Mac I ain’t been slopped once since me weddinday.
1929		M. Prenner ‘More Sl. Words for “Drunk”’ in AS IV:6 441: slopped over.
1932		J.L. Kuethe ‘Johns Hopkins Jargon’ in AS VII:5 336: slopped—intoxicated.
1941		M. Prenner ‘Drunk in Sl.’ in AS XVI:1 Jan. 70/1: slopped (to the ears).
1978		S. King Stand (1990) 973: ‘Everybody knows alcoholism’s a disease.’ [...] ‘Disease, my ass. It’s getting sloppo, that’s what it is.’.