nuthouse
noun
nut·house ˈnət-ˌhau̇s 
slang
: a mental hospital
Example Sentences
Recent Examples on the Web Luther explains that Vanya is on a farm and happy and Diego is in the nuthouse; Allison informs Luther that Klaus has started a cult. 
Rachel Paige, refinery29.com, 3 Aug. 2020 Most of my fellow members of the media laughed at Harry and portrayed him as a stubborn ol’ coot who probably belonged in the nuthouse. oregonlive, 18 May 2020
Rachel Paige, refinery29.com, 3 Aug. 2020 Most of my fellow members of the media laughed at Harry and portrayed him as a stubborn ol’ coot who probably belonged in the nuthouse. oregonlive, 18 May 2020 Word History
First Known Use
1900, in the meaning defined above