Green’s Dictionary of Slang

(US black) an especially acceptable, likeable person.

1935		(con. 1920s) J.T. Farrell Judgement Day in Studs Lonigan (1936) 668: I pity any woman who’d get the idea that you’re a good time.
1983		R. Klein Jailhouse Jargon and Street Sl. [unpub. ms.].