Festivus is a holiday, celebrated on December 23rd, created by Frank Costanza as an alternative to Christmas. He came upon the idea after pummeling a man in the face in a toy-store dispute over a doll (for George). In his own words, "As I rained blows upon him, I realized, 'There must be a better way!'"
It features an aluminum pole instead of a Christmas tree. At dinner, the Airing of Grievances is conducted, in which the celebrants tell each other what the other has done to irritate them that year. The celebration of Festivus does not end until the feats of strength are performed, usually involving George being forced to pin his father.
After Kramer became interested in the idea of "A Festivus for the rest of us," he inspired Frank to begin celebrating the holiday once more, causing great anguish for George, who loathed Festivus. Kramer, Jerry, Elaine, George, Mr. Kruger (George's boss, who had become very interested in Festivus after hearing it mentioned), and several other guests appeared, causing a very socially awkward situation.
The Coruscanti variant of the holiday is celebrated differently than the Seinfeld variant. The holiday starts on December 23rd and ends the next week. The idea was to encompass the celebrations of Christmas and New Years in one week due to the 24/7 work culture of the modern age and give workers time to celebrate the holidays in one week instead of just two (Christmas and New Years)
Instead of the Airing of Grievances. It's replaced by the Burning of Grievances and Misfortunes where people write down what misfortunes have felled upon them and burn the letter on New Years Eve ether privately in one own's fireplace, during the Hatsumōde festival, or mentally.
The Feats of Strength are optional and never performed (It's even discouraged by the Department of Health) though some orthodox followers of Seinfeld still perform the ritual.
Even-though the Hatsumōde Festival is a Japanese Festival and Holiday. It has been incorporated into the Coruscanti Culture and eventually into Festivus itself. Generally, wishes for the new year are made, new o-mamori (charms or amulets) are bought, and the old ones are returned to the shrine so they can be burned during the Burning of Grievances and Misfortunes.
Etymology and origin
Festivus (with long "i", festīvus) is a Latin word, but not the name of a festival: in one reference it is said to mean "festive". A scholarly work on the etymology of the word by Dr. Brian A. Krostenko, summarized in Salkin's book, concludes that in ancient Rome the word evolved, referring at times to the way the common folk would misbehave on official religious holidays and at other times to a certain snooty attitude amongst the higher classes. The book claims, with no proof, that it is possible that the elder O'Keefe, who was studying ancient rituals, knew this etymology and adapted it for his family's holiday. The English word festive derives from festīvus, which in turn derives from festus "joyous; holiday, feast day".
- Also why Coruscantis also adopted the holiday due to the connection with the Ancient Romans