出典:Wiktionary
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.
nitwit (複数形 nitwits)