Originally, kaiawase was played among nobilities as a kind of awasemono (games in which people gather each bringing something of the same kind to decide which is better) in competition for the beautiful coloring, shape, and rarity of the shells, or the superiority of uta (poetry) composed with the shell itself as its subject matter.
本来の貝合わせは、合わせものの一つとして貝殻の色合いや形の美しさ、珍しさを競ったり、その貝を題材にした歌を詠んでその優劣を競い合ったりする貴族たちの遊びであった。