Adeste Fideles
From the Catholic Encyclopedia
A hymn used at Benediction at Christmastide in France and England since the close of the eighteenth century. It was sung at the Portuguese Legation in London as early as 1797. The most popular musical setting was ascribed by Vincent Novello, organist there, to John Reading, who was organist at Winchester Cathedral from 1675-81, and later at Winchester College. The hymn itself has been attributed to St. Bonaventure, but it is not found among his works. It is probably of French or German authorship. It invites all the faithful to come to Bethlehem to worship the new-born Saviour.
JULIAN, Dict. of Hymnology s.v.
JOSEPH OTTEN