'additiment' originates from Latin, specifically the word 'additamentum,' where 'addit-' meant 'added' and '-mentum' was a suffix forming nouns indicating an action or resulting state.

'additamentum' transformed into the Old French word 'aditement,' and eventually became the modern English word 'additiment' through Middle English.

Initially, it meant 'something added,' and this meaning has largely remained the same in modern usage.