'retroactive' originates from Latin, specifically the word 'retroactus,' where 'retro-' meant 'backward' and 'actus' meant 'act or action.'

'retroactus' transformed into the French word 'rétroactif,' and eventually became the modern English word 'retroactive' through Middle English.

Initially, it meant 'acting backward,' but over time it evolved into its current meaning of 'taking effect from a past date.'