There is probably a joke somewhere in here about what name does a Lapdancer use at Christmas but I have no idea what it is.
I take it we are talking traditional Christmas Carols as opposed to onslaught of Christmas Schmaltz….
I will probably plump for “O Come O Ye Faithful”, “We Three Kings” and “Good King Wenceslas”. The later I often use as a trivia puzzle in Christmas Pub Quizzes.