Tamna, or Tamna-guk, was a state based on Jeju Island from ancient times until it was absorbed by the Korean Joseon dynasty in 1404, following a long period of being a tributary state or autonomous administrative region of various Korean kingdoms. The Go (Jeju) clan is the family name of the Grand Duke (Seongju, 성주, 星主), that ruled West Tamna over 400 years. The Moon (Nampyeong) clan is the family name of the Grand Prince (Wangja, 왕자, 王子), that ruled East Tamna for 400 years. The Kingdom of Tamna is also sometimes known as Tangna (탕나), Seomna (섬나), and Tammora. All of these names mean "island country".