Here's a sample:
Holly: The sharply pointed leaves were to symbolize the thorns in Christ's crown and the red berries drops of his blood. Holly became a nativity tradition.
Lump of Coal: According to tradition, giving a lump of coal in the stockings of naughty children comes from Italy.
Merry Christmas: Some priests in Australia advise you to say "Happy Christmas" instead of "Merry Christmas", because Merry has connotations of getting drunk- which brings it's own problems.
Poinsettias: Poinsettias were attached to Christmas starting in 1828. Joel Roberts Poinsett, then the first Mexican ambassador from the United States, imported the plant from Mexico.