The name derives from “chackstones”—stones to be tossed. The knuckle, wrist, or ankle bones (astragals) of goats, sheep, or other animals also have been used in play. Such objects have been found in prehistoric caves in Kiev, Ukraine, and pictures of the game are depicted on jars from ancient Greece.
Excerpt from the entry: Jacks, The Encyclopaedia Britannica
spanishwoods 