Joy to the world wasn’t originally intended to become a Christmas song, Consider that As one of the most joyous of all Christmas hymns, this carol omits references to shepherds, angelic choruses, and wise men. That’s because it was originally intended to describe the second coming of Jesus Christ.
The hymn has more to do with Christ’s second coming than His first, though because the two comings of Christ are historically and theologically connected, the sentiments expressed can apply to both events. The one that has already taken place sets the stage for the other that is yet to happen, an event which true believers eagerly await.