Kegel.

From Middle High German kegel, from Old High German chegil, kegil (“peg”), especially pegs for a tent (zeltchegil) or similar. Middle High German kegel means “peg or pin used for a game” (such as skittles), but regional use from the 14th century onward also preserve a more general meaning of “peg, cudgel”. The etymology cannot be traced with certainty. The word is a member of a Wortsippe which also includes Keil (“wedge”), German Kugel (“ball, sphere”) and Kiel (“keel”). No cognates of Kegel are known outside of German (other than loans from German in Dutch, Scandinavian as well as Baltic and Slavic languages). French quille seems to be a reflex of an Old Frankish form of the word. Proto-Slavic *žezlъ (“stick, staff, rod”) has diverse proposed origins. The German word Keil (“wedge”) is closely related, compared by Grimm to the relationship of Latin cuneus (“wedge”) with cōnus (“cone”). In some dialects, Keil was used as the term for both “wedge” and “bowling pin”. On the other hand, Kroonen suggests a derivation from Proto-Germanic *kagilaz (“cone, pin”), from the root underlying Proto-Germanic *kagô (“trunk”) + *-ilaz (“diminutive suffix, agent suffix”). Also closely related is Kugel (“ball, sphere”). All these terms developed in context of the game of skittles. The relation of Keil to Kegel (both terms for the pin) was the same as that of Kaule to Kugel (both terms for the ball; the former remained dialectal, while Kugel became the generic term for "sphere"). For the development of the sense of an illegitimate son compare German Bengel, Flegel, Balg and the like.