The lost eighth day of the week that was never officially written in the bible. "And after his day of rest and thinking god realized that he had forgotten the most important thing so he said, let there be joy in taste perfection, then majestically god parted the clouds and sent forth eleven angels carrying the burden of a gargantuan platter of nachos."
The Word trianday is derived from the holy shape of nachos.
Guy 1's boss: It's monday why aren't you in work?
Guy 1: Sorry sir but it isn't its trianday and I'm worshipping god by eating nachos on this most holy of days