Io, Saturnalia!

Saturnalia is the Roman midwinter festival, dedicated to the god Saturn, the father of the gods and therefore arguably the most important festival in Rome. It's celebrated from December 17th to the 23rd and included public rites and ceremony and lots of gambling - but most importantly a reversal of social order. For this week in December slaves and their masters essentially switched places. Plebians could pretend to be patricians, and patricians could slum it as plebians. This was the only week that a slave would be invited to speak their mind (as in Plutarch).

The lewd nature of such a festival led to many attempts to outlaw or shorten it (by the piety-obsessed Augustus and the hypocritical Caligula) to no avail.

This is also often attributed as the reason why Christmas is celebrated on December 25th. Previously, the church had marked January 6th as the birth of Jesus. It was changed to December 25th in the fourth century because the pagan converts were already used to celebrating a midwinter festival (in the Empire, mostly Saturnalia but in the outer Provinces like Britain and Gaul the Winter Solstice) around that time. The longest night of the year, December 21st, is customarily celebrated with the use of light and fire. During Saturnalia it was custom to exchange gifts (which were often candles).

So, instead of Merry Christmas or Happy Holidays or Seasons Greetings - why not "Io, Saturnalia"? (Pronounced yo, Sah-tur-na-lia).