'underscore' originates from English, specifically the word 'under' and 'score', where 'under' meant 'below' and 'score' meant 'to mark'.

'underscore' changed from the Old English word 'scoru' meaning 'notch, tally, twenty', and eventually became the modern English word 'underscore'.

Initially, it meant 'to draw a line under', but over time it evolved into its current meaning of 'to emphasize or highlight'.