twiddle (v.)
1540s, "to trifle," of unknown origin, said to be probably imitative; of the fingers, "to twirl idly," first recorded 1670s. Figurative phrase twiddle one's thumbs "have nothing to do" is recorded from 1846; to twirl one's thumbs in the same sense is recorded from 1816. Related: Twiddled; twiddling.