Green’s Dictionary of Slang

1. in pl., money.

c.1760

‘The Rakes of Stony Batter’ in A. Carpenter Verse in Eng. in 18C Ireland (1998) 339: But when their cash is gone, they’ll hunt for a Cully, / And bring the splinters home, to their beloved Bully.

2. a notably thin person.

1839		Crim.-Con. Gaz. 20 Apr. 128/1: I saw Jo Cripper [...] grinning like ‘an old boot in convulsions’ [...] I saw the same splinter playing ‘Billiards’.
1917		R. Lardner ‘The Facts’ in Coll. Short Stories (1941) 456: The other one, Wilma, was a splinter if he ever saw one. You had to keep your eyes peeled or you’d miss her entirely.
1930		R. McAlmon ‘Blithe Insecurities’ in Knoll McAlmon and the Lost Generation (1976) 79: Ain’t you the likely lad? You was a splinter when I last saw you.
1953		J.R. Williams ‘Out of Our Way’ 14 Feb. [synd. comic strip] But lookit this splinter, with no more hips than a starvin’ snake!
1968		J. Alard He who Shoots Last 76: Ya bloody splinter, how’d you like a belt in da ear?