'unrewarding' originates from the prefix 'un-' meaning 'not' and the word 'rewarding', which comes from the Old French 'rewarder', meaning 'to regard or recompense'.

'rewarding' changed from the Old French word 'rewarder' and eventually became the modern English word 'rewarding'.

Initially, 'rewarding' meant 'to give something in return', but over time it evolved into its current meaning of 'providing satisfaction or benefit'.