Green’s Dictionary of Slang

(US) one who has kinky hair, thus usu. a black person.

1926		J.F. Dobie Rainbow in Morning 4: One considers the negro as a shining apostle of sweetness and light, another as a gentle old darkey, and still another as a ‘phallic kinky’.
1942		Berrey & Van den Bark Amer. Thes. Sl.
1983		(con. 1844) I.L. Allen Lang. of Ethnic Conflict 47: Allusions to Other Physical Difference: kinky (1844). Also kink, kinky-head, kinky-nob].