Green’s Dictionary of Slang

1. a castanet, usu. in pl.

1844

C. Cist Cincinnati Misc. 14: Fowler [...] found the truant as he expected at a dance house on Columbia St, with his slippers off, dancing and playing the jaw bones or Castanets [DA].

2. (also jawbone lute) a Jew’s harp.

1845		Knickerbocker (N.Y.) XXVI 336: The frequent sound of the violin, banjo, or jaw-bone lute is [...] an indication [DA].
c.1846		Negro Singer’s Own Book in N.I. White (1928) 34: I’ll set myself in de big armchair / And play on de old jawbone.
1864		J.F. Brobst letter in Brobst Well Mary, Civil War Letters 88: Tell Curt to play Yankee Doodle on the jawbone.
1869		F. Dumont Benedick’s Songster 50: I can play the old jawbone, and can use the fiddlebow [DA].