'self-assurance' originates from the combination of 'self' and 'assurance', where 'self' refers to one's own person and 'assurance' means confidence or certainty.

'assurance' changed from the Old French word 'asseurance' and eventually became the modern English word 'assurance'.

Initially, it meant 'certainty or guarantee', but over time it evolved into its current meaning of 'confidence in oneself'.