'unmodifiable' originates from the prefix 'un-' meaning 'not' and the word 'modifiable' from Latin 'modificare', where 'modi-' meant 'measure' and 'facere' meant 'to make'.

'modificare' transformed into the French word 'modifier', and eventually became the modern English word 'modify', with 'un-' added to form 'unmodifiable'.

Initially, it meant 'not able to be modified', and this meaning has remained consistent in modern usage.