'instinctively' originates from the Latin word 'instinctus,' where 'instinctus' meant 'impulse' or 'instigation.'

'instinctus' transformed into the Old French word 'instinctif,' and eventually became the modern English word 'instinctive' with the adverbial form 'instinctively.'

Initially, it meant 'driven by impulse,' but over time it evolved into its current meaning of 'acting on instinct.'