'antiphrastical' originates from Greek, specifically the word 'antiphrasis', where 'anti-' meant 'against' and 'phrazein' meant 'to speak'.

'antiphrasis' (Greek) passed into Latin and then into English as 'antiphrasis'; the adjective form developed as 'antiphrastic' and the variant 'antiphrastical' appeared in later English usage.

Initially it meant 'speaking against' or 'saying the opposite', and over time it became associated specifically with ironic or contrary expression; the core idea of 'opposite speech' has been retained.