By the fourth century it had come to rank with Easter and Pentecost as one of the three great festivals of the Eastern Church, and its vigil was a day commonly chosen for the baptism of converts. It was first adopted in the Western Church in southern Gaul. There, by the middle of the fourth century, it was kept as a separate festival from Christmas. In Rome it became instead a commemoration of the manifestation of Christ to the Gentiles. The Magi are seen as representative of all the non-Jews to whom Christ came.
Frankincense is, of course, incense and myrrh is a spice used in embalming the dead.
From the few sentences in St Matthew, a whole legend developed in the Middle Ages. The Magi became three in number, were promoted to be kings and finally acquired the names of Melchior, Caspar and Balthazar. Then in 1158 three bodies were found in the Church of St. Eustorgio, just outside a new moat surrounding Milan, which were presumed to be those of the Magi. When the Emperor Frederick Barbarossa captured the city, he took them to Germany, where they were deposited in Cologne Cathedral in 1164. Henceforward the shrine of the Three Kings of Cologne became a famous place of pilgrimage.