Mare — the creature behind the word nightmare
A small, crushing thing that sits on a sleeper's chest in the dark, holding the body still and souring the dream. Norway had a name and a face for sleep paralysis a thousand years before the diagnosis — and that name is buried inside the English word "nightmare."
A sleeper wakes in the dark, eyes open, and cannot move. Something small and very heavy is sitting on the chest, pressing the breath out. This is the mare — what a neurologist now files under sleep paralysis, the body still locked in the muscle-stillness of REM sleep while the mind has come awake — and Norwegians had a name and a face for it a thousand years before there was a diagnosis.
Her name comes from Old Norse mara, kin to the verb merja, to crush. She is older than nearly everything else in the folklore: the court poet Þjóðólfr ór Hvini set a mara in his Ynglingatal before Norway was Christian, somewhere between 870 and 890. The Swedish king Vanlandi lies down at Uppsala and cries out that a mara is treading on him; his men seize his head and she moves to his legs, they seize his legs and she goes back to his head, and he dies between their hands.
By morning she left evidence. Hair was found knotted into tight tangles, and horses came in from the field with their manes plaited and their bodies sweat-dark and trembling, ridden hard all night — marefletter, mare-locks. (A braided mane could also be the nisse’s work, a sign he had taken to the horse; but his braid was a blessing and the mare’s was a wound, and you left both alone.)
The lore carried two versions of her. In one she is her own creature, a small heavy night-being who comes from outside and chooses you. In the other she is a sleeping woman’s spirit slipped loose — the neighbour could be a mare without knowing it, going out at night to ride others and back before dawn. Some families had mares the way others had a weak heart.
Against her the bed was armoured with iron — a knife or open scissors under the pillow, a holed stone hung at the headboard — and shoes were set wrong-way-round at the door to turn her back.
The Old English mære fused into night-mare by around 1300, and the word kept the creature inside it. The German Mahr, the Dutch nachtmerrie, the Swedish mardröm — every time anyone says the word for a bad dream, the mare is in it.