Nutter is a slang term for someone who is crazy, or at least very eccentric. It goes back through most of the 20th century; earlier, it was associated with a more negative or harsh view of someone as really insane: "the nuthouse" was a common term for a mental hospital in both British and US English. Nowadays if you describe someone as a nutter it is usually meant quite affectionately; just that his/ her behaviour is a bit odd.
Related to this are phrases/ words like "nuts" ("he's completely nuts" has the same meaning as "he's a nutter" and there is also "nutty" as in the film "The Nutty Professor."
All these words come from the idea of the head being like a nut, with the contents (brains) being hidden inside a shell (skull.) The idiom "a tough nut to crack" may have the same origin.
Related to this are phrases/ words like "nuts" ("he's completely nuts" has the same meaning as "he's a nutter" and there is also "nutty" as in the film "The Nutty Professor."
All these words come from the idea of the head being like a nut, with the contents (brains) being hidden inside a shell (skull.) The idiom "a tough nut to crack" may have the same origin.
