An Etymological Dictionary of the German Language/Knebel
Knebel, m., ‘branch, peg, moustache, knuckle,’ from MidHG. knębel, m., OHG. knębil, ‘crossbeam, girder, crossbar, cord, fetter, knuckle’; Du. knevel, m., ‘packing stick’; Scand. knefill, m., ‘stake, stick’; Goth. *knabils is wanting. Considering the relation of Goth. *nabala, m., ‘navel,’ to Gr. ὀμφαλός, we may assume for Goth. *knabils, a root gombh (gonbh) in the non-Teut. languages (comp. γόμφος, ‘plug, nail, wedge’; this word, however, is usually connected with the cognates of ModHG. Kamm). — It is still doubtful whether Knebel in Knebelbart ‘(twisted) moustache,’ first recorded in ModHG. and borrowed from LG. and Du., is of a different origin, i.e. connected with AS. cęnep, OFris. kenep, OIc. kanpr (Goth. *kanipa-), ‘moustache,’ MidDu. canefbeen, ‘cheek-bone.’