Green’s Dictionary of Slang

1. (orig. US) a regular, routine, uninspiring job.

1963		in T.I. Rubin Sweet Daddy 14: I could never see myself on a nine to five.
1978		H. Selby Jr Requiem for a Dream (1987) 15: The lames and squares all make it home from the 9 to 5.
1987		Eric B & Rakim ‘Paid in Full’ 🎵 I might just search for a nine to five.
1991		M.B. ‘Chopper’ Read Chopper From The Inside 31: We would be better off with a cut lunch and a nine to five.
2004		K. Jasper ‘Thursday’ in Brooklyn Noir 258: Hard days at bullshit 9-to-5s.
2012		H. Acosta ‘Doing the Job’ in ThugLit Dec. [ebook] ‘[L]eave the [wrestling] business and get a regular nine-to-five’.
2016		D. Whish-Wilson Old Scores [ebook] It felt good to have a nine-to-five.

2. (N.Z. prison) a member of the ‘white-collar’ staff in a prison who work alongside the officers.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 124/2: nine-to-five n. a system person, i.e. a person who works in the prison as a psychiatrist, counsellor, social worker, Ombudsman, etc.