'unsettle' originates from Middle English, specifically the word 'unsettlen,' where 'un-' meant 'not' and 'settle' meant 'to place or fix firmly.'

'unsettlen' transformed into the modern English word 'unsettle,' and eventually became the adjective 'unsettling.'

Initially, it meant 'to disturb or displace,' but over time it evolved into its current meaning of 'causing anxiety or uneasiness.'