"Patapan" (or "Pat-a-pan") is the title of a traditional French (specifically, Burgundian) Christmas carol. The carol revolves around the birth of Jesus Christ, and is told from the perspective of shepherds playing simple instruments—flutes and drums—the onomatopoetic sound of which gives the song its name; "patapan" is meant to mimic the sound of the drum, and an accompanying lyric, "tu-re-lu-re-lu," the flute.
Also known as the antidote to "The Little Drummer Boy,"* here's a cool 2003 rendition of "Pat-a-pan" from the Dale Warland Singers:
*Um, in my own head. Let's just say I hate "The Little Drummer Boy" almost as much as I hate "The 12 Days of Christmas." Do either of those songs end? Ever?