'unleash' originates from Middle English, specifically the word 'lesche,' where 'un-' meant 'not' and 'lesche' meant 'to loosen or release.'

'lesche' transformed into the modern English word 'unleash' through the addition of the prefix 'un-' to indicate the action of releasing.

Initially, it meant 'to release from a leash,' but over time it evolved into its current meaning of 'to release or set free.'