Green’s Dictionary of Slang

rump-and-kidney men n.

[their payment in kind, they were given the leftovers]

fiddlers who play for weddings, feasts, fairs and similar festivities.

[UK]B.E. Dict. Canting Crew n.p.: Rump-and-Kidney-Men c. Fidlers that Play at Feasts, Fairs, Weddings, &c. And Live chiefly on the Remnants, of Victual.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.