As with many of the saints, however, we are able to capture the relationship which Nicholas had with God through the admiration which Christians have had for him—an admiration expressed in the colorful stories which have been told and retold through the centuries.

Perhaps the best-known story about Nicholas concerns his charity toward a poor man who was unable to provide dowries for his three daughters of marriageable age. Rather than see them forced into prostitution, Nicholas secretly tossed a bag of gold through the poor man’s window on three separate occasions, thus enabling the daughters to be married. Over the centuries, this particular legend evolved into the custom of gift-giving on the saint’s feast. In the English-speaking countries, Saint Nicholas became, by a twist of the tongue, Santa Claus—further expanding the example of generosity portrayed by this holy bishop.

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