mist

The noun comes from Middle English mist, from Old English mist, meaning mist, darkness, or dimness of eyesight, which traces back through Proto-Germanic *mihstaz to the Proto-Indo-European root *h₃meygʰ-, meaning cloud, fog, or drizzle. There's also a verb, from Middle English misten, from Old English mistian.

Old English mist already covered more than just weather — it could mean darkness or even a dimness clouding one's sight, a sense the modern word has mostly shed in favor of the purely atmospheric meaning.

It's cognate with Dutch, Swedish, and West Frisian mist, all keeping essentially the same meaning, and more distantly with Sanskrit megha (cloud) and Russian мгла (fog, haze), showing the same root drifting across very different branches of the family.