Kugel.

From Middle High German kugel(e), of unknown origin. It is not clear whether Middle Dutch coghele, coeghele (modern kogel) is a cognate or rather a borrowing from High German. In the former case it would require a Proto-West Germanic *kugulā. Possibly related with English cudgel, from Proto-West Germanic *kuggil, a derivative of Proto-Germanic *kuggǭ (“cog, swelling”), whence German Kogge (“roundish ship”). This group has been compared to words like Lithuanian gugà (“hump”), Albanian gogël (“acorn”), and may be further derived from Proto-Indo-European *gew- (“to bow, bend, arch, curve”). Other German words that may be related to this root include kauern, Keule, Koben, Kuhle, Quaddel. Further discussion The word appears from the Middle High German period referring to a ball used in games, e.g. skittles / bowling. A Swiss dialect form has an additional r, in Krugle, found already in Middle High German in the diminutive form krúgellin (Konrad of Würzburg, d. 1287). Another variant is contracted kūle, kaule, kulle. Low German and parts of West Central German used cognates of Klotz for the ball in skittles. The sense “bullet” is probably an extension of the former use. However, it could theoretically be older than the introduction of firearms, because lead or iron spheres were already used as projectiles fired with slingshots.