The Chinese word 梦魇 (mèngyǎn), meaning "nightmare," is a compound formed by combining two characters: 梦 (mèng), which means "dream," and 魇 (yǎn), which historically refers to a demon or malevolent spirit that was believed to sit on a sleeper's chest, causing suffocation and terrifying visions. This formation is conceptually parallel to the English word "nightmare," which originally denoted a "night" (mare) demon. Therefore, 梦魇 literally translates to "dream demon," capturing both the psychological experience of a bad dream and the ancient folkloric explanation for the phenomenon of sleep paralysis, where the terrifying feeling of being trapped and oppressed in one's sleep was attributed to a supernatural assault.