An Etymological Dictionary of the German Language/Annotated/Kugel
Kugel, feminine, ‘ball, bullet, globe,’ from the equivalent Middle High German kugel, kugele, feminine; compare Middle Low German and Dutch kogel. The word is not recorded in the other languages. It is allied to Modern High German Kaul-, from kûl, kugl, and also to Modern High German Keule, with which English cudgel and Anglo-Saxon cyčgel is closely connected; Keule is a ‘pole with a ball-shaped end.’ Kugel and Kegel cannot possibly be related by gradation.