## Nightmare: The Night Demon
The word *nightmare* is almost universally misunderstood. Most English speakers assume it means 'night horse' — a frightening dream involving, perhaps, a dark mare galloping through the sleeper's mind. The truth is far stranger. The *mare* in *nightmare* is not a horse but a demon — an Old English word for a malevolent supernatural being that sits on sleeping people's chests, crushing them and filling their minds with terror.
### The Mære
Old English *mære* (also *mare*, *mara*) referred to a specific type of nocturnal spirit: an incubus or succubus that visited sleepers, pressed down on their chests, and induced a state of paralysis accompanied by terrifying hallucinations. The experience described is what modern sleep medicine calls sleep paralysis — a state in which the sleeper is conscious but unable to move, often accompanied by a sensation of pressure on the chest and vivid, frightening hallucinations.
The *mære* was not a dream. It was a creature. Medieval people understood the nightmare as an attack by a supernatural entity, not as a product of the sleeping mind. The word *nightmare* originally meant 'the night-mære' — the spirit that comes at night — not 'a bad dream that happens at night'.
The *mære* appears across the entire Germanic world, suggesting a very old mythological figure:
| Language | Word | Meaning | |----------|------|---------| | Old English | *mære* | incubus, nightmare spirit | | Old Norse | *mara* | nightmare spirit, hag | | German | *Mahr* / *Nachtmahr* | nightmare demon | | Dutch | *nachtmerrie* | nightmare (night-mare) | | Norwegian | *mare* | nightmare spirit | | Swedish | *mara* | nightmare |
The Old Norse *mara* appears in the sagas as a shape-shifting spirit that could enter houses through keyholes and sit on sleepers. In Scandinavian folklore, the *mara* was sometimes identified as a living person — often a woman — whose spirit left her body at night to torment others. You could ward her off with iron or by sleeping with your shoes pointed toward the door.
### Into French
The Germanic *mare* even crossed into French, where it combined with Old French *caucher* (to press, to trample — from Latin *calcāre*, to tread) to produce *cauchemar* — literally 'the pressing-mare', the spirit that presses down on sleepers. Modern French *cauchemar* (nightmare) thus preserves the same demon in a Franco-Germanic hybrid.
### The PIE Root
Proto-Germanic *\*marǭ* may descend from PIE *\*mer-* (to harm, to rub away, to die), which also produced:
- Latin *mors* (death) → English *mortal*, *murder*, *mortgage* (death pledge) - Latin *morbidus* (diseased) → English *morbid* - Sanskrit *mara* (death, the demon Māra who tempted the Buddha)
If this connection holds, then *nightmare*, *mortal*, *murder*, and the Buddhist demon *Māra* all share a single prehistoric root — a word for death and harm spoken thousands of years before any of these languages existed.
### Fuseli's Visual Pun
The most famous depiction of a nightmare in Western art is Henry Fuseli's *The Nightmare* (1781), which shows a small demonic figure (an incubus) sitting on the chest of a sleeping woman, while a horse's head with wild, staring eyes peers through the bed curtains. Fuseli was making a visual pun: the painting depicts both the etymological *mare* (the demon on the chest) and the false-etymological *mare* (the horse). The painting became wildly popular, spawning countless imitations and parodies, and it cemented the modern visual association between nightmares and dark, menacing imagery.
### From Demon to Dream
The semantic shift from 'oppressive spirit' to 'bad dream' happened gradually between the fourteenth and sixteenth centuries. As belief in literal nocturnal demons faded, the word *nightmare* transferred from the cause (the creature) to the effect (the terrifying experience during sleep). By Shakespeare's time, *nightmare* could mean either the spirit or the dream, and by the eighteenth century, the creature had been almost entirely forgotten.
Today, *nightmare* is used freely as a metaphor for any terrible experience — 'traffic was a nightmare', 'a bureaucratic nightmare' — with no trace of the medieval demon that gave it birth. The *mære* has been exorcised from its own word.
### What the Word Remembers
But the word still remembers. Every time someone says *nightmare*, they are naming the *mære* — the ancient Germanic demon that crouched on sleeping chests in the dark. The horse was never there. The demon always was.