Etymology 1

From mere, feminine of 'horse' (cf. German Mähre, Dutch merrie), from Proto-Germanic, from Iranian, akin to Sanskrit máryas 'stallion, young man'.

Noun

1. An adult female horse.
2. A foolish woman.
   • 2007, Hester Browne, Little Lady, Big Apple

   The silly mare phoned your mother, talking about applying for a mortgage, and we don't want that, do we?

Etymology 2

, from mera, mære, from *maron (cf. Dutch (dial.) , German (dial.) , Old Norse 'incubus, nightmare', Danish , Swedish ), from Indo-European, akin to Polish 'nightmare', Czech 'nightmare, moth', Old Irish Morrígain 'queen of elves'.

Noun

1. A type of evil spirit thought to sit on the chest of a sleeping person; also the feeling of suffocation felt during sleep; a nightmare.
2. (Shortening of ) A nightmare; a frustrating or terrible experience.

   I'm having a complete mare today.

Noun

1. A dark, large circular plain; a “sea”.
2. On Saturn's moon Titan, a large expanse of what is thought to be liquid hydrocarbons.