Mare
Mare (mâr) , noun
[Old English mere, Anglo-Saxon mere, myre, fem of Anglo-Saxon mearh horse, akin to Dutch merrie mare, German mahre, Old High German marah horse, meriha mare, Icelandic marr horse, OCelt. marka (Pausan. 19, 19,4), Ir. marc, Welsh march. Compare Marshal.]
The female of the horse and other equine quadrupeds.
Mare , noun
[Anglo-Saxon mara incubus; akin to Old High German & Icelandic mara; compare Pol. mora, Bohem. můra.]
(Medicine) Sighing, suffocative panting, intercepted utterance, with a sense of pressure across the chest, occurring during sleep; the incubus; -- obsolete, except in the compound nightmare.
I will ride thee o' nights like the mare.