'unambiguous' originates from the prefix 'un-' meaning 'not' and the word 'ambiguous' from Latin 'ambiguus', where 'ambi-' meant 'both' and 'agere' meant 'to drive'.

'ambiguus' transformed into the English word 'ambiguous', and with the addition of the prefix 'un-', it became 'unambiguous'.

Initially, 'ambiguous' meant 'having more than one meaning', and 'unambiguous' evolved to mean 'having only one clear meaning'.