An Etymological Dictionary of the German Language/Marder
Marder, m., ‘marten,’ from the equiv. MidHG. marder (and mader), m., OHG. mardar, m.; allied to OIc. mǫrðr, ‘marten,’ and AS. mearþ (also meard), ‘marten, weasel’ (without the suffix r, like MidHG. mart, ‘marten’). Whether we are to assume Goth. *marþus or *marþuza remains uncertain. Yet the cognates are probably of genuine Teut. origin (from pre-Teut. martu-), to which MidLat. martus (Ital. martes), with the corresponding Rom. class also point — Ital. martora, Fr. martre, f. (whence E. marten).