'unbordered' originates from the prefix 'un-' meaning 'not' and the word 'bordered', which comes from the Old French 'bordure', meaning 'edge or boundary'.

'bordure' transformed into the Middle English word 'border', and eventually became the modern English word 'bordered'. The prefix 'un-' was added to form 'unbordered'.

Initially, 'bordered' meant 'having a boundary', and with the prefix 'un-', it evolved to mean 'without a boundary'.