 Mackenzie 's explanation of the legend of the blue men was based partly on research into the Annals of Ireland and goes back to the times of Harald Fairhair , the first Norse king , and his battles against the Vikings . The Scottish Gaelic term fear gorm , meaning " blue men " , is the descriptor for a negro according to Dwelly . Thus sruth nam fear gorm , one of the blue men 's Gaelic names , literally translates as " stream of the blue men " , or " river , tide or stream of the blue negro " . Around the 9th century the Vikings took Moors they had captured and were using as slaves to Ireland . The Vikings spent winter months near the Shiant Isles , and Mackenzie attributes the story of the blue men to " marooned foreign slaves " . He quotes an excerpt from historian Alan Orr Anderson 's Early sources of Scottish history , A.D. 500 to 1286 : 
