'unobstructed' originates from the prefix 'un-' meaning 'not' and the word 'obstructed' from Latin 'obstruere', where 'ob-' meant 'against' and 'struere' meant 'to build'.

'obstruere' transformed into the Old French word 'obstruer', and eventually became the modern English word 'obstruct' through Middle English.

Initially, it meant 'to build against or block', but over time it evolved into its current meaning of 'not blocked'.