"fly with back-and-forth motion," 1540s, from flit with frequentative suffix. Flitter-mouse (1540s) is occasionally used in English, in imitation of German fledermaus "bat," from Old High German fledaron "to bat, to flutter." Related: Flittered; flittering. As a noun, from 1892.
flirtatious
flirty
flit
flitch
flite
flitter
flitty
flivver
float
floatation
floater