'sideburn' originates from American English, specifically the word 'burnsides', where 'Burnside' referred to the Civil War general Ambrose Burnside.

'sideburn' changed from the earlier form 'burnsides' (named after Ambrose Burnside, noted for his facial hair); the element order was reversed to 'sideburns', and the singular 'sideburn' developed from that.

Initially, it meant a facial-hair style associated with General Ambrose Burnside, but over time it evolved into its current meaning of a strip of hair grown down the side of the face in front of the ear.