'attestative' originates from Latin, specifically the verb 'attestari' (from the prefix 'ad-' + 'testari'), where 'ad-' meant 'to/toward' and 'testari' meant 'to witness or testify'; the English adjective was formed by adding the suffix '-ative' (from Latin '-ativus').

'attestative' developed in English from the verb 'attest' (via Old French 'attester' < Latin 'attestari') combined with the adjectival suffix '-ative' (from Latin '-ativus'), producing Middle English formations and eventually the modern English 'attestative'.

Initially the root meant 'to bear witness' in Latin; over time the derived English adjective came to mean 'serving to attest' or 'confirmatory' in modern usage.