Green’s Dictionary of Slang

caput adj.

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

finished, over, ruined etc.

[[Ire] ‘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].
[US]J.P. McEvoy Hollywood Girl 171: I mean finis. Capoot.
[UK]A. Sinclair Breaking of Bumbo (1961) 126: It’s done. Finished. Caput.
[US]W. Diehl Sharky’s Machine 129: Point is, it’s done, okay? Corrigon is caput.