From Ancient Greek κᾰκός (kăkós, “bad”).

• (Classical Latin) IPA^(key): [ˈkaː.kʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈkaː.kus]

Cācus m sg (genitive Cācī); second declension

1. (Roman mythology) A fire-breathing giant and son of Vulcan, who was killed by Hercules.

Second-declension noun, singular only.

• “Cacus”, in Gaffiot, Félix (1934), Dictionnaire illustré latin-français, Hachette.
• “Cacus”, in Charlton T. Lewis and Charles Short (1879), A Latin Dictionary, Oxford: Clarendon Press
• “Cacus”, in William Smith, editor (1848), A Dictionary of Greek and Roman Biography and Mythology, London: John Murray