An Etymological Dictionary of the German Language/Moos
Moos, n., ‘moss,’ from MidHG. and OHG. mos, n., ‘moss, moor, swamp’ (whence Fr. mousse, ‘moss’); corresponding to Du. mos, ‘moss,’ E. moss, OIc. mose, m., ‘moss, swamp,’ to which OIc. mýrr (E. mire), ‘slime,’ is allied. To these are related by gradation AS. meós, OHG. mios, MidHG. mies, m. and n., ‘moss,’ whence also ModHG. Mies. The senses ‘moss, swamp,’ may be associated by the connecting link ‘mossy ground,’ hence the assumption of two orig. different words is not required, *mosa-, ‘moss’ (by gradation *miusa, ‘moss,’ OHG. mios, AS. meós, ‘moss’), and mosa-, ‘swamp’ (by gradation *môsa, ‘moor,’ OHG. muor, comp. Meos). Goth. *musa, by gradation *miusa-, ‘moss,’ is connected with OSlov. mŭchŭ ‘moss,’ Lith. mūsaí, ‘mould’ (on liquids), and Lat. muscus, ‘moss,’ which has a derivative c for sc; and also with Gr. μυῖα, ‘horse-fly,’ for μύσια, and μύαξ (for μύσαξ), ‘sea-mussel.’ The meaning ‘swamp’ is still current in Suab. and Bav.; comp. Dachauer Moos.