It is said that he gave away all of his inherited wealth and traveled the countryside helping the poor and sick. One of the best known of the St. Nicholas stories is that he saved three poor sisters from being sold into slavery or prostitution by their father by providing them with a dowry so that they could be married.
Over the course of many years, Nicholas's popularity spread and he became known as the protector of children and sailors. His feast day is celebrated on the anniversary of his death, December 6. This was traditionally considered a lucky day to make large purchases or to get married. By the Renaissance, St. Nicholas was the most popular saint in Europe.
Even after the Protestant Reformation, when the veneration of saints began to be discouraged, St. Nicholas maintained a positive reputation, especially in Holland.
*http://www.history.com/topics/santa-claus#a4
