It’s Going to Be a Very Special Pi Day on March 14, 2015, at 9:26:53 – Slate Magazine
Our pi-themed movement has detoured through pie-themed activities. We now have pie-eating, pie-baking, and pie-throwing contests. The words, pi and pie as they come to us through etymological history, have nothing to do with each other. Pi is simply the English language spelling of the 16th letter of the ancient Greek alphabet. We know it as π, the notational symbol first used by William Jones in the 18th century to denote the ratio of the circumference to the diameter of a circle. Pie, on the other hand, comes to us from … well, it’s not really known where. Even the Oxford English Dictionary is stumped, except to say that it might come from the medieval Latin word for pastry, pia.