Green’s Dictionary of Slang

(US black) a pimp.

1909		J. Washburn Und. Sewer 142: When the P.I.* comes to force his attention upon her, she is almost sure to fall into the trap. [...] *P.I. is an abbreviation for pimp. [Ibid.] 146: The men who live upon women’s earnings do not come from any special class. They are those who are idle, and lazy, and dishonest, and ignorant. From this condition the professional P.I. emerges.
1928		C. McKay Home to Harlem 240: ‘What does he work at?’ [...] ‘He’s a p.i.’.
1931		N. Van Patten ‘Vocab. of the Amer. Negro’ in AS VII:1 30: P-i. M. n. Pimp.
1934		J.L. Kuethe ‘Prison Parlance’ in AS IX:1 27: pee-eye. A pimp.
1935		W. Smith Bessie Cotter 12: She tells him he can be her new pea-eye. [Ibid.] 206: ‘You mean you want to be my pea-eye?’ ‘Manager,’ said Norris. ‘Pimp,’ said Bessie.
a.1942		Z.N. Hurston Harlem Slanguage [vocabulary, typescript carbon in Beinecke Library Yale U.] 1: p.i., a pimp.
1954		(con. 1937) C. Chessman Cell 2455 97: I just don’t think I got the qualifications to be a P.I.
1966		Trimble 5000 Adult Sex Words and Phrases.