Green’s Dictionary of Slang

1. (US black) a small-time, ineffectual pimp; thus anyone of little or no importance.

1969		Cressey & Ward Delinquency, Crime, and Social Process 817: Nearly all young Negro players aspire to reach the position of a ‘big mack,’ but few are qualified to be anything more than a ‘lousy pop corn pimp’.
1979		E. Torres After Hours 24: Popcorn pimp, he didn’t have fifty dollars.
1981		A.K. Shulman On the Stroll 30: Handsome black men in fancy suits and wide-brimmed hats whom prince had contemptuously named ‘popcorn pimps’. [Ibid.] 56: He [...] instilled contempt for the small-time popcorns and respect for the real boss players.
1989		(con. 1982–6) T. Williams Cocaine Kids (1990) 102: Then there are ‘popcorn pimps,’ a term of contempt for men who force women into prostitution, unlike true players who claim to operate with personal magnetism alone.
2018		quarterlyconversation.com 17 Sept. 🌐 [H]e meets a goon [...] who initiates him into the vocation of popcorn pimp—if I may resort to this lovely bit of argot for the description a book so abundant in the same.

2. a man who claims to be, but is not, a pimp.

1980

E. Folb Runnin’ Down Some Lines 250: popcorn pimp [...] 2. Would-be pimp. 3. Phony or fraud.