Hello!
It is pretty confusing but simply put... it has to do with words meaning other words. I’ll give it to you!
In French Happy/Merry Christmas is 'Joyeux Noël'. ... In France, Father Christmas / Santa Claus / St. Nicholas is called Père Noël (Father Christmas). In eastern France he is accompanied by Le Pere Fouettard, a man dressed in black.
So that’s exactly why... if that makes any sense.