An Etymological Dictionary of the German Language/Annotated/nieder
nieder, adverb, from the equivalent Middle High German nider, Old High German nidar, adverb, ‘down, downward’; corresponding to Old Saxon nithar, Dutch neder, Anglo-Saxon niþer, English nether, Old Icelandic niðr; Gothic *niþar, is by chance not recorded. A derivative of the Aryan verbal particle ni, ‘down’ (see Nest), which is preserved in other Teutonic forms (see nied and nieden); compare Old Slovenian nizŭ, ‘below,’ as well as Sanscrit ni, ‘down,’ and Sanscrit nitarâm, which is closely allied to the Teutonic adverb — nieder, as an adjective, ‘nether, lower, base,’ has been recently formed from the adverb Old High German nidari, Middle High German nider, nidere, adjective, ‘nether, low’; akin to Old Saxon nithiri.