'substitution' originates from Latin, specifically the word 'substitutio,' where 'sub-' meant 'under' and 'stituere' meant 'to set or place.'

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

Initially, it meant 'to place under or replace,' but over time it evolved into its current meaning of 'the act of replacing one thing with another.'