nitwit

Etymology

First attested in the 1910s in the US Northeast. Likely from German nit, dialectal form of nichts (“nothing”), or Yiddish ניט (nit), dialectal form of נישט (nisht, “no”), although some dictionaries give the alternative etymology nit (“louse egg; something very small”) + wit.

noun

1. (informal) A scatterbrained or stupid person.
   If you don't remember you are a nitwit. If you do answer, well, you know what the penalty is for perjury. 1918, State Bar Association of Connecticut, Annual Report, page 82
   1921, Emmett Campbell Hall, “Need a Hero be a Nitwit?”, in The Editor, page 58:
   "Don't be a nitwit, honey!" says Adele. "Here, let me open the door! Ma be I did leave them lights on, though it ain't ike me!" 1922, Nina Wilcox Putnam, Laughter Inc