Green’s Dictionary of Slang

1. (US Und.) a prison.

1932

V.F. Nelson Prison Days and Nights 22: They’ve got him in the satchel for fixing cases and grabbing a bunch of cash.

2. (US) the vagina.

1936		(ref. to 1920s) L. Duncan Over the Wall 127: Helen’s smart [...] A good-looking satchel can work miracles with an old twist-crazy guy like the Parole Officer.
1953		Randolph & Wilson Down in the Holler 105: The word satchel is best avoided because it means the pudendum, also known as the pussy, twat, snatch, monkey, moosey, or twitchet.

3. (US) the anus or buttocks.

1962		Ragen & Finston World’s Toughest Prison 816: satchel – The buttocks.
1974		G.V. Higgins Cogan’s Trade (1975) 39: Guy like you that was sticking it in Goat-ass’s satchel.

4. (US, also satch) the scrotum.

[c.1790		‘The Brummagh an Wale’ Luke Caffrey’s Gost 7: He [a horse] has a good store in his Satchel].
2001		OnLine Dict. of Playground Sl. 🌐 satchel, satch n. The male scrotum.

5. (US, also satch) thus used as a term of abuse.

2001

OnLine Dict. of Playground Sl. 🌐 satchel, satch n. [...] An excessively stupid or unpleasant person.

6. see satchel-mouth n.