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

'avert' changed from Latin 'advertere' to Old French/Anglo-French forms (e.g. 'avertir') and Middle English 'averten', and eventually became the modern English word 'avert'.

Initially, it meant 'to turn toward or attend to', but over time it evolved into senses of 'turn away' and 'prevent/ward off'; modern uses reflect both the idea of turning aside and of preventing.