Green’s Dictionary of Slang

egghead n.2

[resemblance]

1. (US) a fool.

[US]O. Johnson Varmint 39: ‘Why, Egghead, howdy-do?’ ‘Ah, there, Butsey White!’ ‘Ta-ta, Saphead.’.
[US]C.S. Montanye ‘Crepe for Suzette’ Thrilling Detective Oct. [Internet] You’re [...] trying to solve the thing yourself, to show what bright little boys newspaper guys are and what a lot of eggheads are cops.
[US]L. Uris Battle Cry (1964) 118: It isn’t funny, egghead.
A Trocchi Cain’s Book 145: Fuck you, egghead!

2. a bald person.

[US]Sun (NY) 6 Dec. 9/6: What with [...] Nero Chink, Zulu Kid, the Dixie Kid [...] Egghead Ratty and London Smoke in pugilism.
[US]‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 13: egg head – Bald headed man, tell him to get a rug!
[UK]N. Griffiths Grits 131: Yull be a fuckin egg-ed afurr tur thurty, so ye wull.
[UK]Guardian G2 5 Oct. 27: Most eggheads don’t share my positive feelings.

3. a bald head.

[US]W.J. Caunitz One Police Plaza 88: Gino’s bald egghead seemed as shiny as ever.
[UK]Guardian G2 10 June 5: Ffion Jenkins [...] fixes her lovely gaze on his funny little egghead.