mare и nightmare

nightmares were widely considered to be the work of demons, which were thought to sit on the chests of sleepers. In Old English, the being in question was called a mare or mære (from a proto-Germanic *marōn, related to Old High German and Old Norse mara), whence comes the mare part in nightmare

У скандинавов - Мара, какое-то существо приходящее по начам и мучающее людей.

> У скандинавов - Мара, какое-то существо приходящее по начам и мучающее людей.

это кошмар -- гибрид кошки и комара

http://ru.wikipedia.org/wiki/Мара_(кошмар)