[ Le Cauchemar (The Nightmare), 1894, by: Eugène Thivier. ]
Immortalizing sleep paralysis. The original definition of sleep paralysis was codified by Samuel Johnson in his ‘A Dictionary of the English Language’ (pub. 1755) as “nightmare”, a term that evolved into our modern definition. Such sleep paralysis was widely considered to be the work of demons and more specifically incubi, which were thought to sit on the chests of sleepers. In Old English the name for these beings was mare or mære (from a proto-Germanic *marōn, cf. Old Norse mara), hence comes the mare part in nightmare. The word might be etymologically cognate to Greek Marōn (in the Odyssey) and Sanskrit Māra.