'addiment' originates from Middle English, specifically the word 'addimentum,' where 'add-' meant 'toward' and '-mentum' was a suffix used to form nouns indicating an action or resulting state.

'addimentum' transformed into the Middle English word 'addiment,' and eventually became the modern English word 'addiment.'

Initially, it meant 'something added,' but over time it became obsolete and is rarely used in modern English.