Looking at nightmare, you might guess that it is a compound formed from night and mare. If so, your guess is correct. But while the night in nightmare makes sense, the mare part is less obvious. Most English speakers know mare as a word for a female horse or similar equine animal, but the mare of nightmare is a different word, an obsolete one referring to an evil spirit that was once thought to produce feelings of suffocation in people while they slept. By the 14th century the mare was also known as nightmare, and by the late 16th century nightmare was also being applied to the feelings of distress caused by the spirit, and then to frightening or unpleasant dreams.
Mommy, I had a really scary nightmare. The party was a complete nightmare.
Recent Examples on the WebOnce inside, people will be terrified by the artwork with haunting faces that change any time anyone walks by. Drape and hang the cloth all over a room or outdoors to transform a space into a nightmare. Angela Belt, House Beautiful, 8 Sep. 2022 Westbrook experienced that kind of failure last season when his homecoming dream transformed into a nightmare. Dylan Hernández, Los Angeles Times, 7 Sep. 2022 One lesson is to prevent this nightmare from spreading elsewhere—such as Taiwan. The Editorial Board, WSJ, 1 Sep. 2022 But the city's ongoing issues with contaminated water — that has been shown to contain E. coli bacteria and lead — has turned the process into a nightmare for the couple. Johnny Dodd, Peoplemag, 1 Sep. 2022 And James Rawlings, a Physics lecturer with Nottingham Trent University, says this would turn any relaxing shower into a nightmare. Joshua Hawkins, BGR, 23 Aug. 2022 This time, a group of childhood friends reunite in Derry, Maine and come face to face with this nightmare known as Pennywise the Clown. Marisa Lascala, Good Housekeeping, 19 Aug. 2022 New federal healthcare price transparency rules empower patients like Jason to avoid this common overbilling nightmare. Josh Archambault, Forbes, 21 June 2022 No telling what's coming next, but more changes have to happen unless the Lakers want to live this nightmare again. Duane Rankin, The Arizona Republic, 12 Apr. 2022 See More