Saint Nikolaus or St. Nicolas is celebrated in European countries and in Germany children put a boot outside the front doors on the night from the 5th to the 6th of December. St Nikolaus fills the boot, called Nikolaus Stiefel with goodies, and at the same time checks up on the children to see if they were good. If they were not, they will have charcoal in their boots instead.
The German-American Thomas Nast and other immigrants popularized their "Saint Nicholas" and other Christmas traditions in America. The tall skinny European St. Nicholas gradually became a fat, jolly, red cheeked old man, with a contracted version of "Saint Nicolas" as his name: Santa Claus.