There is only one Chinese character for the surname Ko. There are ten different Ko clans, but they are all descended from the Ko clan of Cheju Island. There is no historical information regarding the founder of this clan, but there is a legend which tells of three men who appeared from a cave on the north side of Cheju Island’s Halla Mountain. These three men were the founders of the Yang clan, the Pu clan, and the Ko clan, the latter being named Ko Ŭl-la. Some days after the three men emerged from the cave, a box was washed up on the shore of the island. In the box were three women, horses, cows, and agricultural seed. From these beginnings, the three established Cheju Island’s T’amnaguk kingdom and ruled peacefully. Ko is a common surname found throughout the Korean peninsula. Approximately ten percent of Cheju Island’s present-day population consists of members of the Ko family.