Where did the tradition of giving a lump of coal for Christmas originate?
Among the Internet sites I looked up in order to research this question, there seems to be a general agreement that this tradition originated in Italy, where a kindly old witch visits children on the eve of the Epiphany (January 6th) and leave toys and candy for the children in every house. If the child has been naughty during the previous year, she leaves a lump of coal instead of candy. I guess the tradition migrated to the stocking hung up on Christmas Eve as a sort of natural migration, and especially since the secularisation of Christmas has pretty much eliminated celebration of the Epiphany except in a few churches.