saturnalia (n.)Related entries & more
1590s, "time of merrymaking," from Latin Saturnalia, the ancient Roman festivals of Saturn (held in December), a time of feasting and mirthful license for all classes, even slaves; neuter plural of the adjective Saturnalis "pertaining to Saturn," from Saturnus (see Saturn). They correspond to the Greek Kronia.
The extended sense of "period of wild or noisy revelry" is attested by 1782. Related: Saturnalian.