Green’s Dictionary of Slang

(US black) kinky hair.

1902		P.L. Dunbar Jest of Fate (1903) 72: You say dat you couldn’t git a paih of sheahs thoo a niggah’s naps.
1922		‘I Would Not Marry A Black Girl’ in T.W. Talley Negro Folk Rhymes 56: I wouldn’ marry a black gal, / I’ll tell you de reason why: / When she goes to comb dat head / De naps’ll ’gin to fly.
1941		F. Swados House of Fury (1959) 117: If you live on the hill and got straight hair so you don’t have to get your naps busted and kin marry a yella fella and git your pitcher in the paper, sassiety, then you can chew the fat all day long.
1957		R.S. Gold ‘Vernacular of the Jazz World’ in AS XXXII:4 277: naps. Kinky hair.
1985		G. Tate ‘Atomic Dog’ in Flyboy in the Buttermilk (1992) 29: This cat had a lot more on his mind than snipping naps and knotting up doo-rags.
1994		N. McCall Makes Me Wanna Holler (1995) 14: I wondered why my thick, unyielding naps couldn’t be straight and supple.