Green’s Dictionary of Slang

1. (US) to be in complete control and thus assured of victory or success (e.g. as a performer); also as n., something assured of success.

1909		Van Loan Big League 64: Here’s where we lock it up [i.e. a baseball game] in the valise.
1936		D. Burley in Chicago Defender 6 June 23: The Pollyanna Girls ‘locked up up’ at the Savoy Saturday night.
1999		Guardian Guide 26 June–2 July 8: It’s pretty much a Lucas-Spielberg-Cameron lock-up.
2014		Ruderman & Laker Busted 25: Sonia wasn’t afraid to feel or fight. Not girlie fighting [...] but full-throttle punches. She went straight for the face. She could lock it up.

2. (US black) to marry, to maintain a monogamous relationship.

1971		(con. 1930s) G.M. Foster Pops Foster 161: Alma is my second wife and the best thing I ever locked up on [...] I locked up on a good wife.
1978		R. Charles Brother Ray 280: But being deaf and sightless, I wouldn’t know what was going on. I’d probably have to lock up with one woman.

3. (US black) to have under one’s complete control, to possess absolutely.

1944		Cab Calloway New Hepsters Dict. in Calloway (1976) 257: lock up: to acquire something exclusively. Ex., ‘He’s got that chick locked up’; ‘I’m gonna lock up that deal.’.
1944		in ‘Jiver’s Bible’ in D. Burley Orig. Hbk of Harlem Jive.
1974		V.E. Smith Jones Men 88: Stallone tells me the man’s just about got it [i.e. the drug trade] locked up.

4. (US black) of a pimp, to secure the services of a given prostitute.

1981

A.K. Shulman On the Stroll 55: You might catch your girl but fail to lock her, or lock her up but train her wrong.

5. (US prison) to place in solitary confinement.

1980

Jackson & Christian Death Row xvi: Locked up usually means sent to the solitary confinement cells.

6. (US police) to arrest (but not yet place in the cells).

1991		B. McCarthy Vice Cop 75: ‘I locked him up, took him downtown’.
2001		A. Schulman 23rd Precinct 72: ‘One man was using fourteen- and fifteen-year-old kids that we couldn’t lock up for sale’.

7. (US prison) to enter protective custody.

1992

P. Earley Hot House 334: ‘I tell this kid he’s got three choices—he can lock up [go into protective custody], get raped, or protect his manhood’.