'involuntary' originates from Latin, specifically the word 'involuntarius,' where 'in-' meant 'not' and 'voluntarius' meant 'of one's free will.'

'involuntarius' transformed into the Old French word 'involuntaire,' and eventually became the modern English word 'involuntary' through Middle English.

Initially, it meant 'not of one's free will,' and this meaning has largely remained the same in modern usage.