Christmas as we know it is an amalgam of traditions that come from Christianity, older pagan celebrations, and winter customs from various places. It all gets thrown into the mix, including modern traditions like Rudolph the Red-nosed Reindeer. Besides, there are other winter holidays such as Hanukkah, Kwanzaa, New Years Day, winter solstice, and St. Nicholas Day, which all contributed more traditions to our "holiday season." John Green explains a bunch of these traditions and where they came from in the latest mental_floss video.
In case you didn't catch it in time, I'll make it easy for you to find the recording of Jingle Bells from Space.