You might have noticed that the world didn’t end on Dec. 21. Despite apocalyptic readings of the ancient Maya calendar, that date failed to usher in TEOTWAWKI.

No, TEOTWAWKI isn’t some fearsome Maya deity. It’s actually an acronym (pronounced “tee-ought-walk-ee”) that stands for “The end of the world as we know it.” And it is used in all seriousness, online and in real life, by survivalists preparing for a variety of doomsday scenarios, known colloquially as “preppers.”