 Afterwards, it was again invaded by the Avars in the 560s, the Slavs, who first settled c. 480s but became independent only from the 7th century, and the Franks, who named a frontier march the March of Pannonia in the late 8th century.The term Pannonia was also used for a Slavic duchy that was vassal to the Franks.Between the 5th and the 10th centuries, the romanized population of Pannonia developed the Romance Pannonian language, mainly around Lake Balaton in present-day western Hungary, where there was the keszthely culture.