Caʹcus.
A famous robber, represented as three-headed, and vomiting flames. He lived in Italy, and was strangled by Hercules. Sancho Panza says of the Lord Rinaldô and his friends, “They are greater thieves than Cacus.” (Don Quixote.)
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Entry taken from Dictionary of Phrase and Fable, edited by the Rev. E. Cobham Brewer, LL.D. and revised in 1895.