'windfall' originates from Middle English, specifically the words 'wind' and 'fall', where 'wind' meant 'moving air' and 'fall' meant 'to drop'.

'windfall' changed from the Middle English word 'wyndfalle' and eventually became the modern English word 'windfall'.

Initially, it meant 'fruit blown down by the wind', but over time it evolved into its current meaning of 'unexpected gain'.