An Etymological Dictionary of the German Language/Annotated/Marsch
Marsch, feminine, ‘marsh, moor,’ Modern High German only, a Low German word. Low German marsch, Middle Dutch maersche, ‘pasture ground,’ Anglo-Saxon męrsc, masculine, and the equivalent English marsh, Danish marsk, ‘bog.’ Gothic *marisks may be assumed as a derivative of Gothic marei, ‘ocean’ (see Meer); similarly Modern High German Au is a derivative of Gothic ahwa, ‘water.’ Compare Middle Latin mariscus, ‘marsh,’ and some of the Romance words connected with it, such as Old French maresc, Modern French marais, Italian marese, which may, however, be partly derivatives of Latin mare.