We just learned about the Christmas song Joy to the World.
Another famous Christmas song is God Rest Ye Merry Gentlemen, also called Tidings of Comfort and Joy.
This song is very old, and has been found in song books going back before the year 1700 AD.
No one is really sure who wrote the song, but it became very famous after Charles Dickens had it as part of his book A Christmas Carol, where Ebeneezer Scrooge hears carolers singing this and chases them away.
One interesting thing about this song is that the old meaning of "God rest ye merry gentlemen" really meant something like "May God give rest and happiness to the gentlemen", but now these days we think of it more like "May God give rest to the happy gentlemen".
The difference all came when someone moved the comma in the sentence:
Old: God Rest Ye Merry, Gentlemen
New: God Rest Ye, Merry Gentlemen
(from: wikipedia - god rest you merry, gentlemen)
Pentatonix - God Rest Ye Merry Gentlemen (Official Video) - Pentatonix
Kid Facts - Blast from the past: Italian Renaissance