'unattachable' originates from the prefix 'un-' meaning 'not' and the word 'attachable' from 'attach', which comes from Old French 'atachier', meaning 'to fasten'.

'attach' changed from the Old French word 'atachier' and eventually became the modern English word 'attach'.

Initially, 'attach' meant 'to fasten or join', and 'unattachable' evolved to mean 'not capable of being fastened or joined'.