'unstop' originates from English, specifically the combination of the reversative prefix 'un-' meaning 'to remove, reverse (an action)' and the verb 'stop' from Late Latin 'stuppare' meaning 'to plug with tow'.

'unstop' changed from Middle English usage of 'un-' + 'stoppen/stoppe' (from Old English 'stoppian', influenced by Late Latin 'stuppare') and eventually became the modern English word 'unstop'.

Initially, it meant 'to remove a stopper or open something stopped up', and over time it broadened to include 'to clear any obstruction (drains, ears, nozzles)'.