“In dulci jubilo” is macaronic in Latin and German. Its text alternates Latin phrases with Medieval German, creating the mixed-language style associated with the carol.
The title itself means “in sweet rejoicing.” The song is a medieval Christmas carol traditionally attributed to the German mystic Heinrich Seuse, or Henry Suso, and is thought to date from about 1328. A well-known legend says that angels inspired Seuse to sing and dance in worship.
Macaronic songs deliberately combine languages, often pairing a learned liturgical language such as Latin with a vernacular language. In this carol, lines such as “Nun singet und seid froh” (“Now sing and be glad”) appear beside Latin expressions including “in praesepio” (“in the manger”) and “Alpha es et O.”
Later English versions helped spread the melody. Robert Pearsall’s 1837 arrangement retained the Latin while replacing the German, and John Mason Neale’s English version became “Good Christian Men, Rejoice.”