An Etymological Dictionary of the German Language/Annotated/Monat

Monat, masculine (with Modern High German ô from Middle High German â before a nasal, as in Mohn, Mond, Brombeere, ohne, &c.), from the equivalent Middle High German mânôt (d), Old High German mânôd, masculine, ‘month’; compare Gothic mênôþs, Anglo-Saxon mônað, English month. The common Teutonic term mênôþ-, ‘month’ (pre-Teutonic mênôt-), seems identical with Mond, Old Teutonic mênin-. The computation of time according to the periods of the moon is perhaps Old Aryan, since the terms for month in the Aryan languages agree approximately. See under Mond.