Aw, I don't know, I certainly wouldn't use it but it's so out there that I'd probably think it was quite cute, in a bizarre sort of way.
Some data: there were 1371 people given the first name
Christmas in England and Wales between 1837 and 1937. Most of them were boys, but there were quite a few girls too.
Some of the weirder
Christmas combos:
Christmas Twink
Christmas Shepherd
Christmas Holyday
Christmas Holly (x2)
Christmas DickChristmas Doughty
Christmas Cockday
Christmas Bacon
Christmas Angel
There was also a Christmastina, two babies called Christmass and two called Christmasia, and a Christmassy.