realm of the dead in Norse mythology, from Old Norse nifl- "mist; dark" (from Proto-Germanic *nibila-, from PIE root *nebh- "cloud") + heimr "residence, world" (from Proto-Germanic *haimaz, from PIE root *tkei- "to settle, dwell, be home").
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit nabhas- "vapor, cloud, mists, fog, sky;" Greek nephele, nephos "cloud;" Latin nebula "mist, vapor, fog, smoke, exhalation;" German Nebel "fog;" Old English nifol "dark, gloomy;" Welsh niwl "cloud, fog;" Slavic nebo.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit kseti "abides, dwells;" Armenian shen "inhabited;" Greek kome, Lithuanian kaimas "village;" Old Church Slavonic semija "domestic servants;" Old English ham "dwelling place, house, abode," German heim "home," Gothic haims "village."
<a href="https://www.etymonline.com/word/Niflheim">Etymology of Niflheim by etymonline</a>
Harper, D. (n.d.). Etymology of Niflheim. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/Niflheim