We all know today's Christmas is nothing like Christmas in years gone past. In the 17 and 1800's Christmas carolers used to knock on people's doors, sing songs, and demand alcohol and food (sounds like the aftermath of the Rise Guys Christmas Party).
An anthropologist from Sierra College in California thinks he's discovered the original roots of the Santa Claus "myth":
His theory on the origin of the Santa story comes from priests in the Arctic and Siberian region dropping hallucinogenic mushrooms into people's teepees in late December up until the 1700s. He theorizes, "Until a few hundred years ago, these shamans or priests would collect the mushrooms, dry them, and then give them as gifts. Because snow is usually blocking the doors, there was an opening in the roof, thus the chimney story."
That also helps explain the flying reindeer. There are a ton of reindeer in Siberia. They don't fly . . . but if everyone's tripping on shrooms, it's a lot easier to hallucinate and think they're flying.
Most of the rest of the modern Santa Claus story comes from "Twas the Night Before Christmas", which was published in 1823.