An Etymological Dictionary of the German Language/Annotated/Mähre
Mähre, feminine, from the equivalent Middle High German męrhe, Old High German męriha, marha, feminine, ‘mare’; feminine of the Old High German marah, marh, ‘horse,’ discussed under Marschall; compare Anglo-Saxon mýre, English mare, Dutch merrie, Old Icelandic merr, pointing to a Gothic *marhi (genitive *marhjôs). In German the feminine form has been preserved longer than the masculine, on which it is based (compare Frau, Magd, and Schwieger).