An Etymological Dictionary of the German Language/Niere
Niere, f., ‘kidney,’ from the equiv. MidHG. nier, niere, OHG. nioro, m. (OHG. also ‘testicle’); corresponding to Du. nier, f., MidE. and MidLG. nêre (to which are allied E. kidney, MidE. kidenêre, from AS. *cȳ̆dneóre, *cȳ̆dneóra?, ‘kidney’; in Scand. nýra, ‘kidney,’ with i- mutation. If the latter indicates Goth. *niuzô, n., the Teut. class has no further cognates; but if we are to assume Goth. *niurô, niurjô, corresponding forms may be found in the other Aryan languages, which have numerous terms for parts of the body in common with Teut.; Goth. *niurô for *niwrô, *negwrô, from Pre-Teut. *neghrôn, which is represented in Gr. by an equiv. γεφρός, ‘kidney, testicle’ (φ for gh); akin further to Lat. nefrones. With regard to Goth. *niu- for *niw-, *nigw-, see Au.