Every day of the Week in the 365 day year is a holiday of someone's religion, cult or tribe.

Easter is Christian and Christmas is Christian. 

If you want to talk about origins stupidly, part of the U.S Revolution from Britain stems from the rudeness of an American shop keeper who crudely offered a British soldier the job of cleaning the outhouse. 

The U.S Revolutionary War was about being a butt hole. Just like Easter is Pagan, or Christmas is Pagan.