'inestimable' originates from Latin, specifically the word 'inaestimabilis,' where 'in-' meant 'not' and 'aestimabilis' meant 'able to be valued.'

'inaestimabilis' transformed into the Old French word 'inestimable,' and eventually became the modern English word 'inestimable.'

Initially, it meant 'not able to be valued,' and this meaning has largely remained the same in modern usage.