'completion' originates from Latin, specifically the word 'completio,' where 'com-' meant 'together' and 'plere' meant 'to fill.'

'completio' transformed into the Old French word 'complecion,' and eventually became the modern English word 'completion' through Middle English.

Initially, it meant 'the act of filling up,' but over time it evolved into its current meaning of 'the act of finishing something.'