Wikipedia has a great article giving all of the information you could ever want to know about Santa Claus. The current figure we know in popular culture is a creation of several different mythologies that have been combined and altered over the years.
Nicholas was a Bishop who was known for his generosity and kindness to children. At least one miracle was attributed to him by the Catholic Church. The legend began in fourth century Myra in Asia Minor, which today is known as Turkey.
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