According to Torme this was not originally a Christmas song per se and it was released, I think, in of in 1945, Torme and Bob Wells wrote during the summer of 1945.
That is when you write Christmas songs.
Also when you do Christmas specials of what ever kind.
You have to do it then.
I was always working on the special Christmas flavors of Ice Cream in May and deciding how much spice we would need for the eggnog.
If you did not have all your ducks in a row by June you were LATE.
It did kind of take the magic out of things.