Green’s Dictionary of Slang

sleep n.

1. (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].

[UK]D. Lowrie My Life in Prison 63: A year sentence is known as a ‘sleep’.
[Aus]V. Marshall World of Living Dead (1969) 84: Eighteen months! Why, that’s only a sleep compared to some.
[US]‘Dean Stiff’ Milk and Honey Route 199: Bit or jolt – A term in prison. A long stretch is the opposite of a short term or sleep.
[US]Monteleone Criminal Sl. (rev. edn) 212: sleep A one year prison sentence.
[Aus] ‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xl 4/5: sleep: A small prison sentence.
[UK]J. Morton Lowspeak 129: Sleep – 1. (US) a sentence of one year. 2. (UK) a sentence of three years.
[Aus]Tupper & Wortley Aus. Prison Sl. Gloss. [Internet] Sleep. A short sentence.

2. (US black campus) constr. with the, a college lecture.

[US]M.H. Boulware Jive and Sl.

SE in slang uses

In derivatives

sleepville (n.) [-ville sfx1 ]

1. (US) sleep.

Topeka Dly Herald (KS) 17 July 4/3: [headline] ‘On the Trail to Sleepsville’.
[US]Star Trib. (Minneapolis, MN) 10 Sept. 9/2: As paving blocks on the road to Sleepville, insomnia victims try [...] a long brisk walk.
Eve. News (Harrisburg, PA) 6 June 29/8: Sleepville is another vewry important place which demands ten hours of sleep every night.
[US]L.A. Times 5 Sept. 38/4: [advert] JWR Knows What Children Like to Wear En Route to Sleepville.
Plain Speaker (Hazelton, PA) 27 Feb. 19/3: [cartoon caption] ‘I want the scene vacated! Your mother and i are headed for Sleepville!’.
Mean James Journal 12 Oct. at [Internet] Well, I got more shit to do up before I go off to sleepville. Patty’s already in there snoring it up and the cat’s going nuts with her new catnip filled toy I picked up earlier.
Twitter 5 Oct. [Internet] Definitely going to Sleepville soon as I get on this plane. ZZZ.

2. (US) a state of unconsciousness following a knock-out blow.

[US]Pittsburgh Press (PA) 13 Oct. n.p.: A new style caveman bounced to fame [...] champion to the middies in the ring / He send them all to Sleepville with a bing.
Dly Indep. Jrnl (San Rafael, CA) 1 Aug. 15/2: Leo took just one minute and 30 seconds to put George to sleepville as the noisy crowd went wild.

In compounds

sleepless hat (n.) [pun on nap]

a hat on which the nap has worn off.

[UK]Hotten Sl. Dict. 235: sleepless-hats those of a napless character, better known as wide-awakes.