'indistinguishability' originates from the Latin word 'indistinguibilis', where 'in-' meant 'not' and 'distinguere' meant 'to separate or divide'.

'indistinguibilis' transformed into the Old French word 'indistinguible', and eventually became the modern English word 'indistinguishable', with the noun form 'indistinguishability'.

Initially, it meant 'not able to be separated or divided', but over time it evolved into its current meaning of 'impossible to distinguish'.