Saturnalia was originally a feast day for the youngest son of the titans, Saturn.
Although the date has changed throughout course of Roman history, the original date for the feast was December 17th. Saturn’s sibling’s then being one day later.
The holiday is for hounoring Gods, keeping connections with family, and celebrating the beginning of the Solar year. The celebration is actually a week long, and during the early years of the celebration, the Romans participated in a week of lawlessness, where no person could break the law during the week of celebration. Many people drank alcohol and became heavily intoxicated, went from house to house singing naked, and ate human-shaped biscuits!
Sacrifices were introduced. A couch was placed in front of the temple of Saturn and the ropes that bound the statue of Saturn during the rest of the year were untied.
It was introduced around 217 BC to raise morals after war defeats, and originally celebrated for only a day, popularity grew and was extended for a week, until the 23rd of December. The following text is by Seneca the Younger about Rome during Saturnalia.
“It is now the month of December, when the greatest part of the city is in a bustle. Loose reins are given to public dissipation; everywhere you may hear the sound of great preparations, as if there were some real difference between the days devoted to Saturn and those for transacting business… Were you here, I would willingly confer with you as to the plan of our conduct; whether we should eve in our usual way, or, to avoid singularity, both take a better supper and throw off the toga.”
Seneca the Younger 4BC – 65AD
The usual greeting during the celebration was ‘lo, Saturnalia!’. ‘lo’, meaning ‘ho’ being related to Latin, as ‘ho, praise to Saturn!’