English word nightmare comes from Proto-Indo-European *mr-, and later Proto-Germanic *marǭ (Evil (female) spirit; succubus; incubus. Nightmare.)
| Dictionary entry | Language | Definition |
|---|---|---|
| *mr- | Proto-Indo-European (ine) | to die |
| *marǭ | Proto-Germanic (gem-pro) | Evil (female) spirit; succubus; incubus. Nightmare. |
| mare | Old English (ca. 450-1100) (ang) | Nightmare, evil spirit. |
| niȝtmare | Middle English (1100-1500) (enm) | |
| nightmare | English (en) | (figuratively) Any bad, miserable, difficult or terrifying situation or experience that arouses anxiety, terror, agony or great displeasure.. (now, _, rare) A female demon or monster, thought to plague people while they slept and cause a feeling of suffocation and terror during sleep.. A very bad or frightening dream. |