Green’s Dictionary of Slang

foolish, stupid; thus fat-headedness n.

1599		Shakespeare Henry V III vii: What a wretched and peevish fellow is this king of England, to mope with his fat-brained followers so far out of his knowledge!
1603		H. Crosse Vertues Common-wealth n.p.: The lazie Monkes & Fat-headed Friers, in whom was nought but sloth & Idlenes.
1748		Richardson Clarissa VII 108: This I leave to thy own fat-headed prudence.
1771		Smollett Humphrey Clinker (1925) II 160: Besides our company, there was in the house a fat-headed justice of the peace, called Frogmore.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1803		J. Kenney Raising the Wind II i: This fine fat-headed fellow arrested our flight through the town, to put into my hand this letter.
1811		Lex. Balatronicum.
1821		‘An Amateur’ Real Life in London I 399: It must be plain enough to the fat-headed comprehensions of those epicurean persons.
1834		Chester Chron. 7 Feb. 4/5: There are in the Conservative party greedy, gaping, fat-headed fools.
1839		Northern Star 5 Oct. 5/3: Things invented by the Germans [...] in order to humbug the fat-brained English.
1839		Northern Liberator (Tyne & Wear) 16 Nov. 4/5: A set of corrupt, fat-headed [...] muddy brained [...] purse-proud, base, ignorant, un-English fellows .
1846		Leics. Mercury 22 Aug. 4/5: The fat-headed Protectionists share in Partridge’s views.
1855		Berks. Chron. 26 May 4/6: Where is that great fat-headed — of yours?
1855		Dublin Eve. Mail 26 Nov. 2/4: If they close uypon such a bargain, they are fit for nothing else than to be bought and sold like their own fat-brained wethers.
1865		G.A. Sala My Diary in America I 62: The gross, fat-headed brewer, Thrale.
1876		Sheffield Dly Teleg. 13 Sept. 4/2: The plaintiff replied that defendant was ‘a lying scoundrel,’ [...] ‘a fat-headed — ’.
1888		L.A. Dly Herald 26 Oct. 4/3: The intelligent Irishman gives no more for the views [...] of any other fat-breained diplomat.
1889		J.K. Jerome Three Men in a Boat 64: Get up, you fat-headed chunk!
1898		Kipling ‘Stalky’ in Complete Stalky & Co. (1987) 27: Speak the truth, you fat-headed old imposter.
1900		Worcs. Chron. 23 June 8/6: The Mayors and Aldermen of to-day were not the fat-brained gluttons of the old days.
1905		Marvel III:55 14: Well, of all the fat-headed judges in the land, this bounder is the fattest!
1907		W.M. Raine Bucky O’Connor (1910) 207: His chief exploded with low-voiced fury. ‘When I ask your advice, give it, you fat-brained son of a brand blotter.’.
1914		‘Bartimeus’ ‘The Night Watches’ in Naval Occasions 177: Wake up, you fat-headed blighter.
1916		Sun. Times (Perth) 25 June 1s/1: Mr Carper and his fat-brained associates.
1928		C. McKay Home to Harlem 285: A mess o’ fat-headed white soldiers them was knocked off by apaches.
1930		L. Johnson & S. Williams ‘Monkey & Baboon’ 🎵 The monkey and the baboon settin’ on the fence, / Monkey called the baboon a fathead quince.
1933		Yorks. Eve. Post 5 Oct. 6/5: Thick-sculled, beetle-headed, fat-brained, half-witted [...] dolts.
1935		A. Christie Three Act Tragedy (1964) 66: He dodged out of the house while one of the fat-headed constables [...] was taking forty winks.
a.1941		T. Woottwell [perf. Tom Woottwell] ‘Another Attempt to Murder Me’ 🎵 [M]y dear, lovely, fat-headed wife.
1941		C.R. Prance Tante Rebella and her Friends (1951) 157: It was that which made Tante Rebella give tongue, calling the Minister and his She-Inspector a pair of fat-headed foreign frumps.
1953		A. Buckeridge Jennings’ Diary 240: I’ve never met such fatuous fat-headedness in my life!
1960		Wodehouse Jeeves in the Offing 145: You’re talking through the back of your fatheaded little neck.
1962		(con. WWII) J.O. Killens And Then We Heard The Thunder (1964) 94: I’d expect something stupid from a fathead sucker like Bookworm.
1964		H.S. Thompson letter 11 Mar. in Proud Highway (1997) 442: It has taken me a while to get a grip after my fat-headed success in Latin America.
1968		(con. WWII) D. Westheimer Song of the Young Sentry (1969) 143: ‘Because you’re so damn fatheaded it chaps my ass,’ Moran said.
1981		N. Farki Countryman Karl Black 95: Fat-head Charlie could not even read a plan.
1994		T. Fensch Conversations with John Updike xvii: Despite his willingness to grant roughly one out of ten interview requests, Updike told Sanoff that ‘Too much talk can make you fatheaded.’.
2001		G. Morris Parsifal’s Page (2004) 93: ‘Fatheaded dolts!’ At that, the man disappeared behind the wall.