c. 1300, renoun, "fame or glory attaching to a person, place, etc.; reputation," especially good reputation, "state of having an exalted name," from Anglo-French renoun, Old French renon "renown, fame, reputation," from renomer "make famous," from re-, here perhaps "repeatedly" (see re-) + nomer "to name," from Latin nominare "to name" (see nominate).
Medieval Latin had renominare "to make famous;" Old French renominer seems to have meant "name over, repeat, rename." The Middle English verb reknouen, renouen "make known, acknowledge" has been assimilated to the noun via renowned. In old German university slang, a reknowner (German renommist) was "a boaster, a swaggerer."