'unremitting' originates from Latin, specifically the word 'remittere,' where 're-' meant 'back' and 'mittere' meant 'to send.'

'remittere' transformed into the French word 'remettre,' and eventually became the modern English word 'remit' through Middle English. The prefix 'un-' was added to form 'unremitting.'

Initially, it meant 'not sending back or relaxing,' but over time it evolved into its current meaning of 'never relaxing or slackening.'