In the 9th century AD, the Vikings began to settle on Lewis, after years of raiding from the sea. The Norse invaders intermarried with local people and abandoned their pagan beliefs. At that time, rectangular buildings began to supersede round ones, following the Scandinavian style. Lewis became part of the Kingdom of Mann and the Isles, an offshoot of Norway. The Lewis chessmen, found on the island in 1831, date from the time of Viking rule. The people were called the Norse Gaels or Gall-Ghàidheil (lit. "Foreigner Gaels"), reflecting their mixed Scandinavian/Gaelic background, and probably their bilingual speech. The Norse language persists in many island placenames and some personal names to this day, although the latter are fairly evenly spread across the Gàidhealtachd.