An Etymological Dictionary of the German Language/Annotated/Knie

Knie, neuter, ‘knee,’ from Middle High German knie, kniu (genitive knies, kniewes), Old High German chniu, chneo (genitive chnëwes, chniwes), neuter, ‘knee’; compare Dutch knie, feminine, Anglo-Saxon cneó (genitive cneowes), neuter, Middle English cnee, English knee; Gothic kniu (genitive kniwis), neuter, ‘knee’; a common O. and Modern Teutonic word with the primary meaning ‘knee,’ which also belongs to the allied Aryan words; genu-, gonu-, gnu- are the Aryan stems of the word; compare Latin genu, Greek γόνυ (compare γνυ-πετεῖν, γνύξ, ἰγνύαλ), Sanscrit iŭnu, neuter, ‘knee’ (abhijñu, ‘down to the knee,’ jñu-bãdh, ‘kneeling’). This Aryan stem gnu had when declined the variant gnew-, which appears extended in Teutonic by the a of the a-declension, Gothic kniwa-. The shorter Teutonic form knu-, Aryan gnu-, has been retained in Gothic *knu-ssus (inferred from knussjan, ‘to kneel’), ‘kneeling’ (the suffix -ssus is current in Gothic), and probably also in Old Icelandic knúe, masculine, ‘knuckle’ (presupposing Gothic *knuwa, masculine); there are also some abnormal l-derivatives, Middle English cnélien, English to kneel, Dutch knielen, and Swiss chnüle, ‘to kneel.’