caliginous (adj.)

"dim, obscure, dark," 1540s, from Latin caliginosus "misty," from caliginem (nominative caligo) "mistiness, darkness, fog, gloom," which is of uncertain origin. De Vaan's entry for it compares Greek kēlas "mottled; windy" (of clouds), kēlis "stain, spot;" perhaps Sanskrit kala- "black," Latin calidus "with a white mark on the forehead." Related: Calignously; caliginosity.