'extension' originates from Latin, specifically the word 'extensionem,' where 'ex-' meant 'out' and 'tendere' meant 'to stretch.'

'extensionem' transformed into the Old French word 'extension,' and eventually became the modern English word 'extension' through Middle English.

Initially, it meant 'the act of stretching out,' but over time it evolved into its current meaning of 'an addition or prolongation.'