'conclusive' originates from Latin, specifically the word 'conclusivus,' where 'con-' meant 'together' and 'claudere' meant 'to close.'

'conclusivus' transformed into the French word 'conclusif,' and eventually became the modern English word 'conclusive' through Middle English.

Initially, it meant 'to close or finish something,' but over time it evolved into its current meaning of 'proving something beyond doubt.'