Green’s Dictionary of Slang

mullethead n.

(US) a fool.

1884		E. Nye Baled Hay 264: Will the soft-eyed mullet-head please call and get it.
1895		Guthrie Dly Leader (OK) 31 July 2/4: To be read out of a party by 16 mullet-heads [...] is not significant, unless those 16 clowns compose the Populist party in Logan county.
1902		Paducah Sun (KY) 19 Nov. 6/4: Veterans insulted and ignored, and mullet-heads put in the high places.
1906		S.F. Call 5 Aug. 14/3: Only mullet-heads with more money than brains ever get to such off-the-map places.
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 205: mullet-head, a stupid person. ‘If I were she, I wouldn’t waste my time on that mullet-head’.
1934		Z.N. Hurston Jonah’s Gourd Vine (1995) 52: Watch out for Lucy. Git word tuh me iffen any ole mullet-head tries tuh cut me out.
1942		Z.N. Hurston ‘Story in Harlem Sl.’ in Novels and Stories (1995) 1006: I seen you two mullet-heads before. I was uptown when Joe Brown had you all in the go-long last night.
1956		T. Thursday ‘The Big Squawk’ in Smashing Detective Mag. 15 Apr. 🌐 If you dare touch anything, you mullethead, I’ll toss you headfirst into the can.
1978		T. Davies More Aus. Nicknames 71: Mullet Mouth It’s always open.
1989		H. Rawson Dict. of Invective (1991) 49: mullethead. A nineteenth-century Americanism.
2006		email to nytimes.com 27 Dec. 🌐 Florida seems to emit a siren song for every big haired, blond tinted, halfwit mullethead that can’t make it to California.