An Etymological Dictionary of the German Language/Annotated/August
August, masculine, formed, after being based anew on Latin and Romance augustus, from the equivalent Middle High German ougest, ougeste, Old High German augusto, agusto, masculine, ‘August’ (the genuine Old German term is Erntemonat, Old High German aran-mânôt). Compare French août, Italian agosto. It was borrowed in Old High German at the same time as März and Mai.