Excerpts from Books and Wikipedia
"According to a Spanish tradition dating back to the seventh century, St. James the apostle ('Sant' lago' in Spanish) visited Spain during his lifetime to preach the gospel. After his martyrdom in Jerusalem in 44, angels transported the saint's body--miraculously reunited with his severed head--to Spain in a stone boat. . . . St. James was believed to have come to the aid of the victorious Christian army at the Battle of Clavijo (844), and from this time on, the saint was given the epithet Matamoros ('Moorslayer'). . . . By the twelfth century, the cathedral of Santiago at Compostela had become the third most important pilgrimage center in western Christendom." [Furtado: 1001 Days]