'unsettlingly' originates from the word 'unsettle,' which is derived from the prefix 'un-' meaning 'not' and the word 'settle,' which comes from Old English 'setlan,' meaning 'to place or arrange.'

'unsettle' changed from the Old English word 'setlan' and eventually became the modern English word 'unsettle' by adding the prefix 'un-' to indicate negation.

Initially, 'unsettle' meant 'to disturb the arrangement,' but over time it evolved into its current meaning of 'to cause unease or discomfort.'