Saturnalia is the ancient Roman holiday celebrated around the winter solstice.
It was in praise of the
god Saturn, and consisted of a huge drunken
orgy.
Another common practice during this festival was the switching of slave and master roles. for one day, all the slave owners gave up their power to their slaves.
the common saying for this festival (ex. merry
Christmas) was "Io Saturnalia" pronounced "yo saturnalia."