The ritual is connected to the solstice rite of the "new sun" - in the longest nights the "ceppo" burnt to summon the return of heat and light on earth. Pagan rights also used fire as a form of purification of the supposed sins of mankind that had brought the long cold night. The tradition of burning in the fireplace a huge "ceppo" or “ciocco”, usually olive or oakwood, would protect the home from lightning and the ashes spread on the fields would make them fertile.
Between 17 and 24 December in Rome there was the "Saturnalia" festival, in honor of Saturn, the god of agriculture, and there were banquets, gift giving and peace. Then in the year 274 AD emperor Aurelianus officially established the festival called "Dies Natalis Solis Invicti" - birthday of the unconquered Sun - to be celebrated around the 25 December, soon after the winter solstice - and the tradition began of burning for twelve days an oakwood piece in the fireplace.
Since the festival, though pagan, was highly popular also among the Christians, during the 4th century AD the Popes decided to celebrated on the same day the Dies Natalis Domini. The tardition of lighting fires still remains in the colorful, flashing decorations of present-day Christmas.