nightmare

魘 is composed of 厭 (loathe) and 鬼 (ghost). The original meaning of 厭 is satiety. When a person eats too much, they develop an aversion to food and the stomach feels as if it is under pressure; this unpleasant sensation is similar to that of having a nightmare. In addition, encountering a ghost is a surreal experience that feels as if one is in a dream. Therefore, 魘 is used to mean a nightmare.