incubus
n.
c.1200, from Late Latin (Augustine), from Latin incubo "nightmare, one who lies down on (the sleeper)," from incubare "to lie upon" (see incubate). Plural is incubi. In the Middle Ages their existence was recognized by law.
〔蒋〕[cub躺，卧，-us名词后缀;’伏卧于睡眠身上的恶魔”] 梦魔
〔李〕[in-=upon在……之上；cub=to lie down卧；-us n.=thing物→“thing inclined to lie down upon a person喜欢卧在人的身上的东西”→] n. evil spirit supposed to lie down upon sleeping persons;nightmare压在睡眠者身上的恶魔；梦魔