Xmas, Festivus, OR ..?

December 25 is a controversial date in history. Turns out, History has much to say on the matter. Long before it was coined as “Christmas”, pagans celebrated the winter solstice as far back as Sumeria, through Egypt, Greece and of course, Rome. Some say this festive fest is “more fun”. A “Festivus for the rest of us!” Or something.
Speaking of Festivus, the show Seinfeld introduced the term to the world in the infamous episode, “The Strike.” Though just a sub-plot in the episode, the story struck a cord with the audience that lasts to this day. So much, the writers wish they had named the episode, “Festivus” instead.
It was the writers that introduced the concept of “Festivus” via Dan O’Keefe, whom told it to fellow writers as a personal story of oddness. It resonated with them so much, they told it to Jerry, whom insisted it be included in an episode. They included many random references like an “aluminum pole” instead of a christmas tree, and other “events” like the “airing of grievances” and the “feats of strength”. O’Keefe mentioned that all but the aluminum pole were real things his dad thought up. But did his dad just “come up with Festivus out of the blue”? Or does it have roots in the original festivals of pre-Christian times after all?