'paradox' originates from Greek, specifically the word 'paradoxos', where 'para-' meant 'beyond, contrary to' and 'doxa' meant 'opinion' or 'belief'.

'paradox' passed into Late Latin as 'paradoxum' and then into Middle English (via Old French influence) as 'paradox', eventually becoming the modern English word 'paradox'.

Initially it meant 'contrary to expectation or opinion', and over time it has retained that core sense while also broadening to refer to any puzzling or apparently self-contradictory situation or thing.