"Deck The Halls" is what might be called a secular Christmas carol, meaning it has no particular religious content. The melody is actually Welsh, from the 16th century. Mozart used the music in a piano/violin duet, and the words are said to be of American origin, from the 19th Century. The first published version was by the Welsh poet John Ceirog Hughes (1832-87) as Nos Galan - ie New Year's Eve. This poem is totally dissimilar from the song, which was originally a dance. The regular lyrics are believed to have originated with Welsh miners who emigrated to the Appalachians.
I've adapted it ever so slightly for BUG ;)
****REVISED/REFORMATTED NOVEMBER 26, 2019 - SR****
A video for this song: