: a female horse or other equine animal especially when fully mature or of breeding age.

How did nightmare get its name?

Etymology. The word nightmare is derived from the Old English mare, a mythological demon or goblin who torments others with frightening dreams. The term has no connection with the Modern English word for a female horse.

What is the origin of mare?

Etymology. The word mare, meaning “female horse”, took several forms before A.D. 900. In Old English the form was mīere, mere or mȳre, the feminine forms for mearh (horse). The Old German form of the word was Mähre.