The original word being ‘Sinter Klass’ for St. Nicholas came from the Dutch version. The Dutch people who later on got settled in ‘New Amsterdam’ (New York) followed this tradition and introduced it to new people and to new place which is why it got converted to what we now call ‘Santa Claus’.
The Santa Claus what is portrayed now is because of the famous picture by Thomas Nast in 1881, is from visualizing the poem ‘A Visit From St. Nicholas‘ written by Clement Moore in 1822. Which is now more familiarly known as ‘A Night Before Christmas’.
St. Nicholas would help the needy by giving gold coins which is why the most of Europe would believe in giving gifts and presents to each other on the 6th of December but somehow the feast day got related to 25th December. As the birth of Jesus was unknown, Pope Julius I decided to Christianize the celebrations where a night before Christmas St. Nicholas would give sweet, chocolates and goodies in each and every house as a good sign and a good beginning. Which was practiced and it spread out as a tradition.