An Etymological Dictionary of the German Language/Kugel
Kugel, f., ‘ball, bullet, globe,’ from the equiv. MidHG. kugel, kugele, f.; comp. MidLG. and Du. kogel. The word is not recorded in the other languages. It is allied to ModHG. Kaul-, from kûl, kugl, and also to ModHG. Keule, with which E. cudgel and AS. cyčgel is closely connected; Keule is a ‘pole with a ball-shaped end.’ Kugel and Kegel cannot possibly be related by gradation.