In the Viking era beginning circa 793, the Norse raiders often captured and enslaved militarily weaker peoples they encountered. The Nordic countries called their slaves "thralls" (Old Norse: "Þræll"). The thralls were mostly from Western Europe, among them many Franks, Frisians, Anglo-Saxons, and both Irish and Britonnic Celts. Many Irish slaves travelled in expeditions for the colonization of Iceland. The Norse also took German, Baltic, Slavic and Latin slaves. The slave trade was one of the pillars of Norse commerce during the 9th through 11th centuries. The 10th-century Persian traveller Ibn Rustah described how Swedish Vikings, the Varangians or Rus, terrorized and enslaved the Slavs taken in their raids along the Volga River. The thrall system was finally abolished in the mid-14th century in Scandinavia.