early 13c., from Old English leogere "liar, false witness," agent noun from Anglian legan, West Saxon leogan "be untruthful, lie" (see lie (v.1)). "The form in -ar is probably in imitation of the refashioned forms such as scholar for scoler and pillar for piler." [Barnhart][liar etymology, liar origin, 英语词源]