Where did the popular Christmas carol featured in the commercial "Christmas Bells" originate?
Christmas Bells (advertisement):  The advertisement, produced with stop-motion animation, features Hershey's Kisses, fashioned as a handbell choir, playing the Christmas carol "We Wish You a Merry Christmas". We Wish You a Merry Christmas: "We Wish You a Merry Christmas" is a popular English Christmas carol from the West Country of England.
West Country of England