noun
or os·tra·kon ˈästrəˌkän
( plural ostra·ca or ostra·ka -rə̇kə)
Etymology: Greek ostrakon
1. : a potsherd used as a ballot in the ancient Athenian practice of ostracism
2. : a fragment of pottery or limestone containing a written inscription
that the Hebrews … wrote freely on papyrus, parchment and potsherds is apparent from large finds of ostraca — I.M.Price