'disjoint' originates from Old French, specifically the word 'desjoindre,' where 'des-' meant 'apart' and 'joindre' meant 'to join.'

'desjoindre' transformed into the Middle English word 'disjointen,' and eventually became the modern English word 'disjoint'.

Initially, it meant 'to separate or disconnect,' and this meaning has largely remained the same in modern usage.