From the LCMS website:
Of the many saints commemorated by the Christian Church, Nicholas (d. A.D. 342) is one of the best known. Very little is known historically of him, although there was a church of Saint Nicholas in Constantinople as early as the sixth century. Research has affirmed that there was a bishop by the name of Nicholas in the city of Myra in Lycia (part of Turkey today) in the fourth century. From that coastal location, legends about Nicholas have traveled throughout time and space. He is associated with charitable giving in many countries around the world and is portrayed as the rescuer of sailors, the protector of children, and the friend of people in distress or need. In commemoration of “Sinte Klaas” (Dutch for Saint Nicholas, in English “Santa Claus”), December 6 is a day for giving and receiving gifts in many parts of Europe.