Green’s Dictionary of Slang

bones n.2

[? the traditional ‘Nigger Minstrel’ line-up which featuredMister Bones playing percussion, Tambo playing tambourine and Mr Interlocutor at the centre]

(US) a black person.

[[UK]Empire (Sydney) 27 July 2/6: The minstrels sat in a row of which the two extremities were respectively occupied by Mr Pell [...] himself was ‘bones’ — for the word at last came to denote the player as well as the instrument].
[[UK]Cheshire Obs. 26 Nov. 6/5: Edward Davies, the ‘bones’ of a street nigger party, was charged [...] at the Marlborough-street Police-court].
[[Aus]Bulletin (Sydney) 6 Oct. 25/1: The old Christy Minstrels show at St. James’s Hall, London, went bung recently. [...] ‘Pony’ Moore started life as the ‘bones’ of the burnt cork crowd, and was probably a humorist in his time].
[US]Van Loan ‘Excess Baggage’ Score by Innings (2004) 404: Doctor Bones reminded me. ‘Good land, chief [...] I neveh did git no chance to doctah that man’s ankle.’.
[US]Wentworth & Flexner DAS.
[US]Bentley & Corbett Prison Sl. 54: Bones A black person.