'unfruitful' originates from the prefix 'un-' meaning 'not' and the word 'fruitful', which comes from the Old English 'fruteful', meaning 'producing fruit'.

'fruteful' transformed into the Middle English word 'fruitful', and eventually became the modern English word 'unfruitful' with the addition of the prefix 'un-'.

Initially, it meant 'not producing fruit', but over time it evolved into its current meaning of 'not producing good or useful results'.