The numerous miracles St. Nicholas is said to have wrought, both before and after his death, are outgrowths of a long tradition. There is reason to doubt his presence at Nicaea, since his name is not mentioned in any of the old lists of bishops that attended this council. His cult in the Greek Church is old and especially popular in Russia. As early as the sixth century Emperor Justinian I built a church in his honour at Constantinople, and his name occurs in the liturgy ascribed to St. Chrysostom. In Italy his cult seems to have begun with the translation of his relics to Bari, but in Germany it began already under Otto II, probably because his wife Theophano was a Grecian.
With such a popularity, his legends inevitably became intertwined with others. In Germanic countries, it sometimes became hard to tell where the legend of Nicholas began and that of Woden (or Odin) ended. Somewhere along the line, probably tied to the gold-giving story, people began giving presents in his name on his feast day. When the Reformation came along, his following disappeared in all the Protestant countries except Holland, where his legend continued as Sinterklass. Martin Luther, for example, replaced this bearer of gifts with the Christ Child, or, in German, Christkindl. Over the years, that became repronounced Kriss Kringle, and ironically is now considered another name for Santa Claus.
Sources:
1) Catholic Encyclopedia. "St. Nicholas of Myra." Accessed December 20, 2011. http://www.newadvent.org/cathen/11063b.htm.
2) Christian History.net. "The Real St. Nicholas." Accessed December 20, 2011. http://www.christianitytoday.com/ch/news/2004/nick.html
