Pope Sylvester I is traditionally celebrated on this day. Also called Silvester, he was pope from January 31, 314 to December 13, 335. He served as the bishop of Rome at a crucial era in the history of Christianity, during the reign of Constantine I and the emergence of the Arian controversy, that involved matters pertaining to Christology and the Trinity.
Seven swans a'swimming represented the seven-fold gifts of the Holy Spirit which are Prophesy, Serving, Teaching, Exhortation, Contribution, Leadership, and Mercy.
For the full history of the 12 Twelve Days of Christmas click here!