Green’s Dictionary of Slang

1. (US tramp) a ‘part-time’ tramp, who can and will opt out of the lifestyle when he wishes.

1930

‘Dean Stiff’ Milk and Honey Route 215: Sweet back—A hobo sheik who is only sampling hobo life.

2. (US black) a pimp.

a.1942

Z.N. Hurston Harlem Slanguage [vocabulary, typescript carbon in Beinecke Library Yale U.] 1: sweet-back, a pimp.