The term Avernus (plural Averni) was also used by ancient naturalists for certain lakes, grottos, and other places which infect the air with poisonous steams or vapors. They were said to be frequent in Hungary on account of the abundance of mines there. The Grotto dei Cani in Italy was a famous example. The most celebrated of these, however, is Lake Avernus.
They were also called mephites. Mephitis was the Roman goddess of noxious vapors, who protects against malaria. The adjective "mephitic" means "foul-smelling" or "malodorous".
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