The Epiphany is the manifestation of Christ to the Gentiles as represented by the Magi (Matthew 2:1–12).
History of Epiphany: A Fourfold Feast
Epiphany originally celebrated four different events, in the following order of importance: the Baptism of the Lord; Christ’s first miracle, the changing of water into wine at the wedding in Cana; the Nativity of Christ; and the visitation of the Wise Men or Magi. Each of these is a revelation of God to man: At Christ’s Baptism, the Holy Spirit descends and the voice of God the Father is heard, declaring that Jesus is His Son; at the wedding in Cana, the miracle reveals Christ’s divinity; at the Nativity, the angels bear witness to Christ, and the shepherds, representing the people of Israel, bow down before Him; and at the visitation of the Magi, Christ’s divinity is revealed to the Gentiles—the other nations of the earth.
The End of Christmastide
Eventually, the celebration of the Nativity was separated out, in the West, into Christmas; and shortly thereafter, Western Christians adopted the Eastern feast of the Epiphany, still celebrating the Baptism, the first miracle, and the visit from the Wise Men. Thus, Epiphany came to mark the end of Christmastide—the Twelve Days of Christmas (celebrated in the song), which began with the revelation of Christ to Israel in His Birth and ended with the revelation of Christ to the Gentiles at Epiphany.