'highly' originates from the Old English word 'hēahlic,' where 'hēah' meant 'high' and '-lic' was a suffix forming adjectives.

'hēahlic' transformed into the Middle English word 'highliche,' and eventually became the modern English word 'highly'.

Initially, it meant 'in a high manner,' but over time it evolved into its current meaning of 'to a great degree or extent'.