nightmare

the word 'nightmare' has a direct and literal origin in old english folklore. it is a compound of 'niht' (night) and 'mare', a term for a malevolent spirit or incubus believed to sit upon the chests of sleepers, causing feelings of suffocation and dread. this supernatural entity was thought to be the direct cause of terrifying dreams and the associated physical sensation of paralysis. over time, the word's meaning generalized, first to the distressing dreams themselves and later to any intensely frightening or anxiety-inducing experience, shedding its explicit supernatural connotations while retaining the core sense of nocturnal terror.

Structure: night + mare night (old english 'niht', meaning 'the dark part of a 24-hour period'), mare (old english 'mare', meaning 'an evil spirit thought to lie upon and suffocate sleepers').