Green’s Dictionary of Slang

1. (US black) any blacks who are the first to take on a specific job in a formerly all-white world.

1994

C. Major Juba to Jive.

2. the first chance, the first opportunity; often as excl. firsts! I want to do something first!

1953

J. Thompson Criminal (1993) 75: I was going to call him myself if you hadn’t got firsts on the phone.