Decorating One Room: A commonly mis-transcribed song is Deck the Hall. When this song was written, the word "hall" referred to the main socializing room in the castle, palace, or other building. We make the same use of the term today in such designations as dining hall, lecture hall, and concert hall. A hallway designated a corridor leading to the hall. Nowadays, of course, we have shortened hallway to hall and thus think of the average palace as having several of them. But, when the song calls for decking (decorating) the hall, it means the central room, not the corridors, so hall originally was, and should now remain, singular.

The Phantom Calling Birds: The popular Christmas song The Twelve Days of Christmas originated as a children's "memory and forfeits game" in which the first to forget a line must drop out of the game. According to most current versions of this song, on the fourth day of Christmas the singer received "four calling birds." Did you ever wonder what, exactly, a calling bird was? A parrot that spends too much time on the phone, perhaps?
     Well, there is no such animal as a "calling bird." As you can confirm by looking at older songbooks, especially those printed in England, the proper term is "colley birds," which are a type of blackbird.
     Since this mistake consists of but a single word, I suppose it doesn't qualify as a mondegreen.

The Golden Birds: Another curiosity about The Twelve Days of Christmas is why her true love would give a gift of jewelry in the middle of a series of gifts of birds.

But it all makes perfect sense if you understand that "gold rings" are a reference to ring-necked pheasants, not bands of precious metal.
     In this case, the music publishers get the words right, but the illustrations are often wrong.

Starting Christmas: Speaking of the 12 Days, a commonly held misunderstanding is that they begin 12 days prior to Christmas and end, therefore, on Christmas day. The opposite is correct. December 25 marks the start of the period and January 6th the end.
     This supposedly commemorates the 12 days between the birth of Jesus and the arrival of the esteemed visitors from "the east" (i.e., Persia, now Iran.) Those who wonder about a caravan making such a long trek in such a short time might be interested in the commentary about the historical accuracy of the Biblical accounts to be found here.

Wise Star Seers: Just who were these intrepid travelers? The popular song, written around 1860 by John H. Hopkins, Jr., speaks of three kings from the Orient. This reflects a tradition dating back at least to a 6th-century Latin text that named them Gaspar, Melchior, and Balthazar. Neither their number nor their royal status are supported by the original tale as told by Matthew:

     The idea that there were three visitors comes from the citing of three gifts they brought; the idea of them being kings comes from men trying to elevate their religious hero. Today's more accurate translations of Mathew's ancient Greek refer to the visitors as neither kings nor wise men, but astrologers.
    Hopkins decision to promote the more dramatic fiction is understandable as he was writing We Three Kings for a Christmas pageant at the New York Theological Seminary where he taught music. (This seems to be the same school where Clement C. Moore taught oriental literature some 30 years previous.)

Dating Christmas: There are only two hints in the Christian Bible as to when Jesus was born. The first is Luke's mention of a decree from Emporer Augustus regarding a general registration during Quirinius' reign as governor of Syria. Unfortunately, there is no record of such a decree and there are myriad reasons to doubt that one ever was issued.
     But Luke gives us another hint. When Jesus was born, he says, there were shepherds nearby watching over their flocks through the night. This implies that the birth occurred either in the spring (when the sheep were giving birth) or in mid-summer (when it was too hot to be out during the day).
    All scholars agree that the decision to celebrate Jesus' birth at the end of December was made to compete with various Roman and pagan celebrations of the winter solstice — that is, of the rebirth of the sun.