'attest' originates from Latin, specifically the word 'attestari', where 'ad-' meant 'to' and 'testari' meant 'to bear witness'.

'attest' changed from Latin 'attestari' into Late Latin/Old French forms such as 'attester' and Middle English 'attesten', eventually becoming the modern English 'attest' and its derivative 'attested'.

Initially, it meant 'to bear witness' or 'to testify', but over time it has come to mean more broadly 'to declare or confirm something as true' or 'to certify authenticity'.