. . . that to "deck the halls" means to decorate the house with all sorts of greenery (not just boughs of holly) and to do so before Christmas Eve is considered bad luck?
Source: The Great American Christmas Quiz Check this site for answers to the questions posed. They open in a conveniently scripted window.
For instance: Did you know where we got the "X" in "Xmas"? It's really from Christ's name in the Greek language, Xristos.
