'Avernus' originates from Latin, specifically the word 'Avernus', ultimately reflecting a Greek form 'Aornos' (Ἄορνος or Ἄορνος), where the Greek prefix 'a-' meant 'without' and 'ornis/ὄρνις' meant 'bird' (hence 'birdless').

'Avernus' appears in Latin writings referring to the lake near Cumae; the name comes via Greek usage ('Aornos') describing the place where birds would not fly, and it entered English usage as the proper name 'Avernus' in classical and later literary references.

Initially, the name emphasized the literal idea of 'birdless' (because fumes from the crater were said to kill birds); over time it became established as the proper name of the lake and, by literary extension, a poetic term for the underworld.