This French Christmas character, the ‘whipping father’, said to accompany Santa on his rounds on 6th December, is fortunately no longer heard of much in French tradition.
An incentive to behave, he was covered in coal and dressed in black, and would whip or spank naughty children whilst Santa handed out presents to the good ones.
There are various stories about his origins.
In one, an innkeeper gruesomely kills the sons of a wealthy landowner to rob them of their money. When St. Nicholas discovers this, he brings the children back to life and forces Le Père Fouettard to become his assistant as punishment for his sins.