51 days until christmas!!!

I honestly have no idea, I'm looking through the lyrics and it doesn't have a name.

The horse's name is Bobtail.
Bells on Bobtail ring, making spirits bright.

You probably found a poor transcription. I've seen a few that said "bells on bob tails ring." Why would there be plural tails, if it's a one horse open sleigh?

Ohhhhh, I thought bobtail was the old fashioned word for a string or the tail of a horse.
True, well the more you know.

Bobbing a tail is one of many grooming techniques/styles used with horses, but in this case, it's also the name of the horse.

Sweet! You learn something new everyday :)