Green’s Dictionary of Slang

belfry n.

the head.

1897		North American (Phila., PA) 26 July 4/3: If you would be up to date don’t tell a man he has trolleys in his head; but impress upon him the fact that he has ‘bats in his belfry.’.
1907		Times Dispatch (Richmond, VA) 10 Mar. 55/1: ‘You must think the Boss is as balmy in the belfry as you blue lobsters’.
1908		B. Fisher A. Mutt in Blackbeard Compilation (1977) 40: There is no doubt that the accused had a few screws loose in his belfry.
1911		H.S. Harrison Queed 84: Something loose in his belfry, as ye might have surmised from them damfool tax-drools.
1911		S. Ford Torchy 17: Ah, brush your belfry! [...] Your mind needs chloride of lime on it.
1919		St Louis Post Dispatch (MO) 17 Aug. 47/6: Anybody who can think a theatrical syndicate out of $225,000 [...] has no flaws in his belfry.
1927		Eve. Teleg. (Dundee) 8 Sept. 3/2: We are sure getting an ache in the belfry figuring out how he gets that way.
1930		R. McAlmon ‘Blithe Insecurities’ in Knoll McAlmon and the Lost Generation (1976) 61: People get old sitting on their behinds while they rot in their belfries.
1933		C. Drew ‘Gorilla Grogan’ in Bulletin (Sydney) 26 July 40/2: ‘[H]e don’t take his thinkin’ exercises too regular’ [...] ‘Cobwebs in the belfry?’.
1939		Howsley Argot: Dict. of Und. Sl.
1960, 1975		Wentworth & Flexner DAS.
1977		E. Torres Q&A 87: Think I’m crazy in the belfry?