'undissolvable' originates from the prefix 'un-' meaning 'not' and the word 'dissolvable', which comes from Latin 'dissolubilis', where 'dis-' meant 'apart' and 'solvere' meant 'to loosen'.

'dissolubilis' transformed into the Old French word 'dissoluble', and eventually became the modern English word 'dissolvable', with 'un-' added to form 'undissolvable'.

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