'nitwit' originates from English, specifically a jocular combination of 'nit' (meaning a louse egg or something very small/insignificant) and 'wit' (meaning intelligence).

'nit' and 'wit' were combined in colloquial English to form 'nitwit' (recorded in the early 20th century in informal usage), and the plural 'nitwits' follows regular plural formation.

Initially coined as a humorous or derogatory compound meaning 'a person of little wit', it has retained essentially the same meaning of 'foolish person' into modern usage.