Where does “nightmare” come from?

nightmare (Middle English) comes from Old English nihtmare, from Proto-West Germanic nahtmarā, from Proto-West Germanic naht, from Proto-Germanic nahts, from Proto-Indo-European nókʷts, from Proto-Indo-European negʷ- — bare, naked.

Ancestry of “nightmare”, step by step

StepLanguageWordMeaning
1Old Englishnihtmaremare; nightmare
2Proto-West Germanicnahtmarānightmare
3Proto-West Germanicnahtnight
4Proto-Germanicnahtsnight
5Proto-Indo-Europeannókʷtsnight
6Proto-Indo-Europeannegʷ-bare, naked
Every word from Proto-Indo-European negʷ- →Every word from Proto-Indo-European nókʷts →Every word from Proto-Germanic nahts →