"female horse," Old English mere (Mercian), myre (West Saxon), fem. of mearh "horse," from Proto-Germanic *markhjon- (cf. Old Saxon meriha, Old Norse merr, Old Frisian merrie, Dutch merrie, Old High German meriha, German Mähre "mare"), said to be of Gaulish origin (cf. Irish and Gaelic marc, Welsh march, Breton marh "horse"). No known cognates beyond Germanic and Celtic. As the name of a throw in wrestling, it is attested from c.1600. Mare's nest "illusory discovery, excitement over something which does not exist" is from 1610s.