Nicholas was the fourth-century bishop of Myra. Our modern depiction of the saint as Santa Claus giving gifts in stockings or shoes most likely stems from Nicholas secretly tossing a bag of gold (to be used as dowries) through a poor man’s window on three separate occasions so the man's three daughters could be married. 

Learn more at https://www.franciscanmedia.org/saint-of-the-day/saint-nicholas