caput, adj. — Green’s Dictionary of Slang

caput adj.

also capoot

[Ger. kaputt, done for; also milit. use as ‘stolen’ during WWI ]

finished, over, ruined etc.

[1788		‘The Vicar and Moses’ Chap Book Songs 4: Good people let’s pray, put the corpse tother way; [...] ’Tis best to take care tho’ the sages declare, / A mortum caput can’t tremble].
1930		J.P. McEvoy Hollywood Girl 171: I mean finis. Capoot.
1959		A. Sinclair Breaking of Bumbo (1961) 126: It’s done. Finished. Caput.
1978		W. Diehl Sharky’s Machine 129: Point is, it’s done, okay? Corrigon is caput.