Antiphrasis is the rhetorical device of saying the opposite of what is actually meant in such a way that it is obvious what the true intention is.
[1] Some authors treat and use antiphrasis just as irony, euphemism or litotes.
[2] When the antiphrasal use is very common, the word can become an auto-antonym,[3] having opposite meanings depending on context.
For example, Spanish dichoso[4] originally meant "fortunate, blissful" as in tierra dichosa, "fortunate land", but it acquired the ironic and colloquial meaning of "infortunate, bothersome" as in ¡Dichosas moscas!, "Damned flies!".
[5][6] Some euphemisms are antiphrasis, such as "Eumenides" 'the gracious ones' to mean the Erinyes, deities of vengeance.