Green’s Dictionary of Slang

1. (US) stupid.

[c.1597		Shakespeare Henry IV Pt 1 II iv: Why, thou clay-brained guts, thou knotty-pated fool, thou whoreson].
1885		C.A. Siringo Texas Cow Boy (1950) 103: We suceeded in finding two little knotty-headed two-year old steers.
1907		Hickman Courier (KY) 5 July 1/4: A few knot-headed, surfeited politicians have woven a web of laws.
1919		Twelfth US Infantry 80: Well, I’m a knotty-headed hound!...You sure are a prize package as a K.P.! [HDAS].
1921		Coconino Sun (Flagstaff, AZ) 20 May 1/5: How any set of men can get so knot-headed and make such a bone-headed break [...] is hard to imagine.
1931		E.M. Berry ‘Sawmill Divertissements’ in Botkin Folk-Say 219: Saron had a sawmill and that meant it was town to them knot-headed boys from Glenwood.
1947		W.D. Overholser Buckaroo’s Code (1948) 54: Cotton [...] looked at the frozen-faced Harriman, the knot-headed Deuce Hinson.
1953		W.G. Ogilvie Cactus Village 46: You cursed knotty-head beast, why make you poison me goat?
1969		Glenn Orhlin ‘Bawdy Strawberry Roan’ [folksong] I found myself hired / T’ snap out some bronc’s / This roan stud had sired / Their knot-head cayuse’s / Just like their Dad.
1975		J. D’Costa Escape to Last Man Peak 6: Nellie-knotty-’ead-never-combed-’er-’air.
1984		J.K. Van Dover Murder in the Millions 133: A man initially responsible for military progress [...] in spite of opposition from the knotheaded liberals.
1994		Artifacts Between A Rock And A Hard Place [album] ‘Attack Of New Jeruzalem’ 🎵 I’m nice on mic jacks, and murder to a dub deck / The Knotty Headed ruffneck, Tame don’t give a fuck yet.
1996		Mobb Deep Hell On Earth [album] ‘Can’t Get Enough Of It’ 🎵 Knot headed niggaz get knocked out a lot.
2002		A. Satterfield Ground Effect 135: I want you to know, Tim, that you haunted your knotheaded father during that time.

2. (US black) having tightly curled hair.

1887		Wkly Irish Times 5 Feb. 1/4: American Wit and Humour [...] She will flirt with all the best young men [...] and finally marry some knotty-headed Jim Crow.
1934		J. Peterkin Roll, Jordan, Roll 159: She was a black, knotty-headed little thing, ’bout six year old.
1937		Z.N. Hurston Their Eyes Were Watching God (1998) 9: Dere wuz uh knotty head gal name Mayrella.