'attestor' originates from Latin, specifically from the verb 'attestari', where the prefix 'ad-' meant 'to/toward' and 'testari' meant 'to bear witness'.

'attestor' passed into Medieval Latin as 'attestator' and via Anglo-French/Old French forms into Middle English (also attester), eventually becoming the modern English 'attestor'.

Initially it meant 'one who testifies or gives evidence', and over time it has retained essentially the same meaning as 'a person who attests or bears witness'.