'unconvincing' originates from the prefix 'un-' meaning 'not' and the word 'convincing', which comes from Latin 'convincere', where 'con-' meant 'together' and 'vincere' meant 'to conquer'.

'convincere' transformed into the Old French word 'convaincre', and eventually became the modern English word 'convince', with 'un-' added to form 'unconvincing'.

Initially, 'convincere' meant 'to conquer together', but over time it evolved into its current meaning of 'persuade'. Adding 'un-' negates this meaning.