'ad' originates from the Latin word 'advertere', where 'ad-' meant 'toward' and 'vertere' meant 'to turn'.

'ad' changed from the Latin word 'advertere' to the Old French word 'advertir', and eventually became the modern English word 'advertisement', which is often shortened to 'ad'.

Initially, it meant 'to turn attention toward something', but over time it evolved into its current meaning of 'a public notice promoting something'.