Green’s Dictionary of Slang

(US) a psychiatric institution.

1914		‘High Jinks, Jr’ Choice Sl. 75: A cozy corner in the nuttery for yours.
1920		Wodehouse Coming of Bill (2004) 77: It takes all kinds of ivory domes to make a nuttery. I ran across a new brand of simp this morning.
1930		‘Dean Stiff’ Milk and Honey Route 62: Should the sociotechnic social worker be convinced that you are not normal she will have you bound for the nuttery before sunset.
1950		Goldin et al. DAUL 1471/2: Nuttery. An institution for the criminally insane or for mentally defective delinquents.