Green’s Dictionary of Slang

1. (US) get moving!

1945

in T. Shibutani Derelicts of Company K (1978) 362: O.K., you guys, hit it!

2. (US prison) be quiet!

1967

M. Braly On the Yard (2002) 82: ‘What’re you going to do on the variety show [...] Perform on the meat whistle?’ ‘Hit it, punk’ Nunn said. ‘I wouldn’t move in on your specialty.’.