Green’s Dictionary of Slang

1. (orig. US) orange juice.

1934		Wodehouse Right Ho, Jeeves 168: Was it not you who threw away that o.j.?
1946		De Vries & Bushkin ‘Boogie Woogie Blue Plate’ 🎵 You can hear her calling orders like this [...] ‘OJ up wreck two in a cup’.
1978		R. Price Ladies’ Man (1985) 183: I bought a rum and o.j.
1994		G. Indiana Rent Boy 101: I drink a quart of OJ.
1999		T. Dorsey Florida Roadkill 78: Serge [bought] a quart of OJ.
2001		I. Rankin Falls 145: Rebus was getting his OJ topped up.

2. (US drugs, orig. milit.) marijuana laced with opium [O n. (2) + j n. + pun on sense 1 above].

1982		(con. 1970) J.M. Del Vecchio 13th Valley (1983) 28: The O-Js were thin, perfectly rolled marijuana cigarettes soaked in an opium solution.
2001		ONDCP Street Terms 16: O.J. — Marijuana.

3. (US black) a large car, typically a Ford or Lincoln [proper name O.J. Simpson (b.1947), the former football hero turned film star who advertised such cars for Hertz c.1980, prior to his 1995 murder trial].

1979		Sugar Hill Gang ‘Rapper’s Delight’ 🎵 Ya say im gonna get a fly girl / gonna get some spankin / drive off in a def OJ.
1980		N. George ‘Rapping Deejays’ in Buppies, B-Boys, Baps and Bohos (1994) 46: ‘OJ’ is a reference to a big car. Erstwhile football star [...] OJ Simpson does Hertz commercials featuring Ford and Lincoln Mercury cars.