The name of the dish comes from the Middle High German kugel meaning "sphere, globe, ball"; thus the Yiddish name likely originated as a reference to the round, puffed-up shape of the original dishes (compare to German Gugelhupf-a type of ring-shaped cake).
While Litvaks (Jews from Lithuania, northern Poland and northern Russia) call the pudding "kugel," Galitzianers (Jews from southeastern Poland and the western Ukraine) call it "kigel."