Green’s Dictionary of Slang

solid n.

[someone or something that has substance, thus dependable, trustworthy]

1. constr. with the, a guinea.

[UK]Harris’s List of Covent-Garden Ladies 60: [She] cares not how much she drains him of his liquid treasure, but will be content with one piece of the solid.

2. (UK tramp) the road.

[UK]Partridge DSUE (8th edn) 1112/2: [...] C.20.

3. (US Und.) a trustworthy fellow criminal or prison inmate.

[US]H. Yenne ‘Prison Lingo’ in AS II:6 280: Two birds (men) solids of mine (true pals, who will not tell) meet in Chi. (Chicago).

4. (US black) a favour, usu. in phr. do (someone) a/the solid, to perform a favour.

[US] ‘Honky-Tonk Bud’ in D. Wepman et al. Life (1976) 55: Say, you look sick, like you need a fix, / Perhaps I can do some solids for you.
[US]Eble Campus Sl. Mar. 1: Do me a solid – Do me a favor.
[US]R. Price Blood Brothers 119: If I ever got like that, and I asked you to check me out, would you do me the solid?
[US] W. Safire What’s The Good Word? 83: The help would be forthcoming in light of the fact that you did me a ‘solid’ (a favor).
[US](con. early 1950s) J. Ellroy L.A. Confidential 393: Give me an answer on this, and if I like it I’ll owe you a solid.
[US](con. 1970s) G. Pelecanos King Suckerman (1998) 254: Tate did me one big solid today.
[US]Simon & Pelecanos ‘Bad Dreams’ Wire ser. 2 ep. 11 [TV script] Do yourself a solid here, Mike.
[US]A. Mansbach ‘Crown Heist’ in Brooklyn Noir 128: Do me a solid and mind the store, bro.
[US]G. Pelecanos (con. 1972) What It Was 172: The Rosens did you a solid by hiring you.
[US]D. Winslow The Force [ebook] ‘Do me a solid, though. Give Levin an assist’.