The celebration of Epiphany ("the manifestation of the Lord") predates the celebration of Christmas. It encompasses a range of themes, including the coming of the Magi ("the Three Kings"), the Baptism of Christ and the marriage feast at Cana. It is a major feast: the liturgical colour is white, and there are six candles on the altar.
In the western church, Twelfth Night (Epiphany Eve, January 5th) had come by the early middle ages to celebrate the visit of the Magi. That they were foreigners reminds us of the universality of the Christmas message. At the same time, the themes of Christ's Baptism and the marriage feast at Cana were transferred to the following two Sundays of Epiphany.
The Finnish word "Loppiainen” dates from the 1600s, and is used because Epiphany marks the end of the Christmas holiday (”loppu” = ”end”). The season of Christmas, however, continues with the Sundays after Epiphany, the number of which depends on the date of Easter.