'proportion' originates from Latin, specifically the word 'proportio', where 'pro-' meant 'for' and 'portio' meant 'part or share'.

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

Initially, it meant 'a part or share', but over time it evolved into its current meaning of 'the relationship of one thing to another in terms of quantity, size, or number'.