Green’s Dictionary of Slang

(US Und.) serving time in prison.

1852		G.C. Mundy Our Antipodes I 111: [of transportation] That implicit trust which those who have never ‘been down’ have a right to respect.
1937		‘Boxcar Bertha’ Sister of the Road (1975) 214: My old pimp [...] got pinched for carrying some junk in to a prisoner, ands he’s been down at Atlanta for five years.
1960		C. Himes Big Gold Dream 104: I’ve been down so long that down don’t worry me.
1977		E. Bunker Animal Factory 12: You’ll look like Gina Lollobrigida to some of those animals who’ve been down for eight or nine years.
1985		J. Sullivan ‘To Hull and Back’ Only Fools and Horses [TV script] Oh I’ll have him down.
1997		Simon & Burns Corner (1998) 147: I mean, she stood by me when I was down.
2002		J. Lerner You Got Nothing Coming 13: What’s up, dawg? Whatchu down for this time?
2013		J. Stahl Happy Mutant Baby Pills 28: Son, I was down while you were still boosting Slurpees from the 7-Eleven.