'oneself' originates from Middle English, specifically the combination of 'one' and 'self', where 'one' meant 'a single person or thing' and 'self' referred to 'a person's essential being'.

'oneself' changed from the Middle English word 'oneself' and has largely retained its form and meaning in modern English.

Initially, it meant 'a person's own self', and this meaning has largely remained the same in modern usage.