'indefeasible' originates from Middle English, specifically the word 'indefesible,' where 'in-' meant 'not' and 'defesible' meant 'capable of being annulled.'

'indefesible' changed from the Old French word 'indefesible' and eventually became the modern English word 'indefeasible'.

Initially, it meant 'not capable of being annulled,' and this meaning has largely remained the same in modern usage.