incubus

The story

1. Latin · derived fromincubō“nightmare, one who lies down on the sleeper”
2. Late Latin · borrowed fromincubus
3. English todayincubus

From Late Latin incubus, from Latin incubō (“nightmare, one who lies down on the sleeper”), from incubō (“to lie upon, to hatch”, from in- (“on”) + cubō (“to lie down”)).