Green’s Dictionary of Slang

1. (orig. US) to pass, to approve, to ‘give the go-ahead’.

1888		Missouri Republican 25 Jan. n.p.: Please O.K. and hurry return of my return [DA].
1896		Ade Artie (1963) 65: I didn’t think you’d O.K. the scheme.
1908		‘O. Henry’ ‘The City of Dreadful Night’ in Voice of the City (1915) 141: So they draws up open-air resolutions and has them O.K.’d by the Secretary of Agriculture.
1917		Hall & Niles One Man’s War (1929) 250: Day after to-morrow I go to Kerenski’s office to have him O.K. my passport.
1929		E. Dahlberg Bottom Dogs 176: Lorry peered over the shoulder of a fella who had just been o.ked.
1931		D. Runyon ‘Gentlemen, the King!’ in Runyon on Broadway (1954) 173: The lawyer says he will okay anything Saro has to say to me 100 percent.
1942		G. Marx letter in Groucho Letters (1967) 18: All this has been okayed by the Hays Office.
1956		I. Fleming Diamonds Are Forever (1958) 100: Charge the ticket to me. I’ll okay it.
1960		C. MacInnes Mr Love and Justice (1964) 161: He’s gone sick, and our doctor has okayed it. Ulcers, he says.
1975		E. Torres Carlito’s Way 95: I won’t okay their credit.
1989		(con. 1982–6) T. Williams Cocaine Kids (1990) 119: At first he said no, but that paper is powerful, so he okayed it.
2001		Indep. Rev. 17 Feb. 20: Pyroplastic was OK’d by my word-processor spell-check.

2. (US) to pay someone’s bill.

1944		D. Runyon Runyon à la Carte 24: I am personally loaded at this time and I am [...] pleased to okay Mike with Marie for the last of her three rooms.
1959		E. De Roo Go, Man, Go! 8: ‘Your—your father OK it?’ ‘He helped me pick it out, but I put down the money.’.