The Strange History Behind the Word Nightmare

A lot of people think that the “mare” in “nightmare” refers to a horse—like the one ominously poking its head past the curtain in Swiss painter Henry Fuseli’s 1781 painting The Nightmare, one of the most iconic (and appropriately nightmarish) depictions of the subject ever created.

However, this is not the case. The real origins of the word “nightmare”—obscured by the passage of time and the rise of different contemporary connotations—can be found in another part of the painting: namely, the equally unsettling goblin crouching on the sleeping woman’s chest. 

Goblins and Nightmares

In England and other parts of medieval Europe, such goblins were known as mares: demons from folklore that were said to sit on people’s chests at night, causing a terrible, suffocating feeling and bad dreams. 

“Mare” itself can be traced back to the Old English “mera,” the Proto-Germanic “maron,” and—ultimately—the Proto-Indo-European root “mer,” meaning “to harm” or “to die.” From this ancient root also derive the Czech word “mura,” the Polish “zmora,” and the Irish “mór,” to name just three examples.

This root is also the source of the German “Mahr” and the Old Norse “mara.” These both translate to “incubus”—a word that describes a male demon and derives from the Latin “incubare,” which means “to lie upon.” The imp in Fuseli’s painting is typically referred to as an incubus.

The other meaning of “mare”—an adult female horse, zebra, or other equine species—likewise stretches back to the distant past: to the Proto-Germanic “marhijo” (the source of the Old Saxon “meriha,” the Old Norse “merr,” and the Dutch-Frisian “merrie”) and, beyond that, to the Proto-Indo-European “márkos.” 

A History of Bad Dreams

In early modern England, nightmares were associated with witchcraft and the Devil, and women who were visited by these demonic creatures were said to be at risk of transforming into witches themselves. Merlin, the sorcerer of Arthurian legend, was said to have been the child of an incubus, among other historical and folkloric figures.

The two distinct meanings of the word “mare” are not always easily separated. An early definition of the word “nightmare” from the 14th century refers to an evil spirit “afflicting men (or horses) in their sleep.” The French word for nightmare, “cauchemar,” features the Old French “cauche,” which derives from the Latin “calco,” meaning “to trample.”

Over time, the word “nightmare” stopped referring to the supernatural creature believed to cause bad dreams and came to refer to the dreams themselves. Since the early 1900s, the word has not only referred to bad dreams, but also to waking life situations that people wish were bad dreams, such as accidents or misfortunes.