Songfacts®:

• "Deck The Halls" is what might be called a secular Christmas carol, meaning it has no particular religious content. The melody is actually Welsh, one of many fine Welsh melodies that have been adapted for English folk songs, like "The Ash Grove." Having said that, the song has a truly international pedigree; Mozart used the music in a piano/violin duet, and the words are said to be of American origin, from the 19^th Century.
• The first published version was by the Welsh poet John Ceirog Hughes (1832-87) as Nos Galan - i.e. 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 immigrated to the Appalachians. >>>

  Suggestion credit:
  Alexander Baron - London, England, for above 2
• Since this song can be performed royalty-free to capture the spirit of the season, it shows up in a lot of TV shows and movies. A few examples include The Big Bang Theory, The Office, The Nightmare Before Christmas, Halloween (sung by Bing Crosby), and Emma.
  
  The song played a key role in the movie A Christmas Story, where the family is forced to eat their dinner at a Chinese restaurant, where the staff does their best to sing this for them, but can't because their accents make "Fa la la la la" sound like "Fa wa wa wa wa." There was also a 2006 movie called Deck The Halls starring Danny DeVito and Matthew Broderick as neighbors who feud over their Christmas displays; Gary Ho-Ho-Hoey did the title song in that one.
• There are 12 "Fa la la la la la la la la"s in this song, making a total of 96 "La"s.
• In 1999 SheDaisy's version of "Deck the Halls" reached #61 on the Hot 100 after it appeared appearing in the end credits of Disney's 1999 direct-to-video film, Mickey's Once Upon a Christmas.
• Nat King Cole recorded the carol for his 1960 album The Magic of Christmas. Sixty years later, his rendition entered the Hot 100 for the first time, peaking at #43.
• Mannheim Steamroller re-imagined the carol as a synth-pop instrumental on their first Christmas album in 1984.