'untreatable' originates from the prefix 'un-' meaning 'not' and the word 'treatable', which comes from the Latin word 'tractare', meaning 'to handle or manage'.

'tractare' transformed into the Old French word 'traiter', and eventually became the modern English word 'treat'. The prefix 'un-' was added to form 'untreatable'.

Initially, 'tractare' meant 'to handle or manage', but over time, 'treat' evolved to mean 'to care for medically', and 'untreatable' now means 'not able to be treated'.