'repeatedly-proven' originates from Modern English, combining the adverb 'repeatedly' (derived from 'repeat' + suffix '-ly', ultimately from Latin 'repetere') and the past participle 'proven' (from the verb 'prove', ultimately from Latin 'probare').

'repeat' changed from Latin 'repetere' (re- + petere) via Old French and Middle English into the modern English 'repeat'; 'prove' changed from Latin 'probare' via Old French 'prover' and Middle English into 'prove' and its past participle 'proven'. The compound adjective form arose in Modern English by combining the adverb and the past participle.

Initially, components meant 'do again' ('repeat') and 'test/try/approve' ('prove'); over time 'prove' shifted toward 'demonstrate truth' or 'show to be true', so the combined phrase now means 'shown to be true many times'.