kaioke' is a kind of bucket used to keep clamshells for 'kaiawase' (a Heian period game which involved pairing the two parts of clamshells) or 'kaioi' (an old name of kaiawase game in the Heian period, which involves pairing the two parts of clamshells) played from the Japanese medieval period to the Edo period.
貝桶とは、日本の中世から江戸時代にかけて伝わる遊戯の貝合わせや貝覆いに用いる貝殻の入れ物である。