Green’s Dictionary of Slang

the end, finality; usu. in phr. It’ll be curtains for you.

1901		T.A. Dorgan in Zwilling TAD Lex. (1993) 29: I got tired and tried to hold on, but I couldn’t find anything. Gee whiz; I thought it was curtains.
1916		J. Lait ‘The Gangster’s Elegy’ in Beef, Iron and Wine (1917) 250: Well, that’s the blow-off. Here’s curtains for you, Gene the Greek.
1923		H.C. Witwer Fighting Blood 170: He knew that if the champion discovered what he had done to Smith’s jaw, he’d simply crack him there again and it would be curtains.
1936		J.T. Farrell World I Never Made 393: There was a satisfaction in punching some sonofabitch square in the jaw like that, calling curtains on him in one punch.
1947		B. Schulberg Harder They Fall (1971) 43: That was curtains for Danny as a fighter.
1958		A. Sillitoe Sat. Night and Sun. Morning 191: If you or any of your pals come back to the bait, it’s curtains for ’em.
1960		D. Lytton Goddam White Man 17: That Afrikaner man is a man for his cattle; touch my cow you touch me; and a coloured boy fooling with cows is asking for curtains.
1973		A. Bennett Habeus Corpus Act II: Otherwise, one word and it’s curtains, finito.
1983		J. Sullivan ‘Thicker than Water’ Only Fools and Horses [TV script] Thank Gawd for that! I thought it was a medical term for curtains!
1997		(con. 1950s) J. Byrne Slab Boys [film script] 27: Another peep out of you, Farrell, and it’s curtains, capeesh?
2000		Sun. Times Mag. 6 Feb. 15: After one evening with Tony I knew it was curtains for Carl.
2011		P. Tatchell on ‘Excess Baggage’ BBC Radio 4 If anything had happened to me I'd have been curtains.
2017		1011 ‘No Hook’ 🎵 Fucking with me that’s curtains.