kneeyoudaoicibaDictYouDict[knee 词源字典]
knee: [OE] The majority of modern European words for ‘knee’ go back to a common Indo- European ancestor which probably originally signified ‘bend’. This was *g(e)neu or *goneu, which lies behind Latin genu ‘knee’ (source of French genou and Italian ginocchio, and also of English genuine) and may well be connected with Greek gōníā ‘angle’, from which English gets diagonal.

It passed into Germanic as *knewam, which over the centuries has diversified into German and Dutch knie, Swedish knä, Danish knoe, and English knee. The derivative kneel [OE] was formed before the Anglo-Saxons reached Britain, and is shared by Dutch (knielen).
=> genuine, kneel[knee etymology, knee origin, 英语词源]
knee (n.)youdaoicibaDictYouDict
Old English cneo, cneow "knee," from Proto-Germanic *knewam (cognates: Old Norse kne, Old Saxon kneo, Old Frisian kni, Middle Dutch cnie, Dutch knie, Old High German kniu, German Knie, Gothic kniu), from PIE root *g(e)neu- (cognates: Sanskrit janu, Avestan znum, Hittite genu "knee;" Greek gony "knee," gonia "corner, angle;" Latin genu "knee"). Knee-slapper "funny joke" is from 1955.
knee (v.)youdaoicibaDictYouDict
early 13c., "to bend the knee, kneel," from Old English cneowian, from cneow (see knee (n.)). The meaning "to strike with the knee" is first recorded 1892. Related: Kneed; kneeing.