caliginous

The story

1. Middle French · borrowed fromcaligineux“misty; obscure”
2. English todaycaliginous

Borrowed from Middle French caligineux (“misty; obscure”), or directly from its Latin etymon cālīginōsus (“misty; dark, obscure”). Cālīginōsus is derived from cālīgō, cālīginis (“fog, mist, vapour; darkness, gloom”)) + -ōsus (suffix meaning ‘full of, prone to’ forming adjectives from nouns).