In Dulci Jubilo (Lyrics)
From HymnWiki
In Dulci Jubilo (Latin for "In sweet jubilation") is one of the most famous medieval macaronic carols. (It is also the name of the carol's tune.) It apparently began as a mixed Latin-German text. It is also well-known in an English-only version beginning "Good Christian Men, Rejoice", translated by John Mason Neale.