Green’s Dictionary of Slang

diaper n.

1. (US black) a sanitary napkin.

1980

E. Folb Runnin’ Down Some Lines 197: There are expressions related to pregnancy, menstruation, birth control, and female hygiene: [...] sling shot, diaper (sanitary napkin); diaper the baby (put on one’s sanitary napkin).

2. (N.Z. prison) a newly graduated prison officer.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 55/2: diaper n. a new prison officer recently completed his or her training.

SE in slang uses

In compounds

diaper viper (n.)

(US) a child molestor, a paedophile.

2009

J. Stahl Pain Killers 270: He some kind of chomo? A diaper viper?

In exclamations