I put Holly for this one as "The holly bears the berry as red as any blood" and I couldn't think of anything better. Perhaps someone else can, but too late for me because I have sent mine already. May have been in too much of a hurry!
It would have to be either Halle or Berry then as it is only one word with 5 letters. If pushed, I would pick Berry as I cannot think of any way in which Halle can be connected to Christmas whereas Berry could be.