Green’s Dictionary of Slang

sleep n.

1. [1910s+] (UK/US/Aus.) a short term in prison [the UK/US versions are somewhat longer, about twelve months, than the Aus., which is three months].

2. [1940s] (US black campus) constr. with the, a college lecture.

SE in slang uses

In derivatives

In compounds

sleepless hat (n.) [pun on nap]

[mid-19C–1900s] a hat on which the nap has worn off.

sleepwalker (n.)

[1940s] (Aus.) a sneak-thief.