In slang, they're referred to as "bones"
[DOC] [TLE] 50 Slang Terms for Money - Daily Writing Tips [PAR] Here's a roster of slang synonyms in plural form for words for US currency in 
particular, ... Bones: dollars (origin unknown) .... minted in 1815, a sum of twenty-
one shillings was still referred to as a 'guinea' when my father was young (1950s
); ... For example, The new tires are good, but I'm not sure they're worth a buck 
and a... [DOC] [TLE] Have you heard the expression Pizza "Bones" [Archive] - Straight ... [PAR] (We used it to refer to the crust that some people don't eat.)