Shut your pie hole

I remember the first time I saw the Food Network. It was back when it was first invented, when they were still showing Japanese episodes of Iron Chef. I'm like "A whole network for cooking shows? That'll never catch on."
A television staple in the Brockway house, and just about the only Food Network show I watch now that they don't sell episodes of the Japanese Iron Chef is Alton Brown's Good Eats. Alton doesn't just give recipes and show how to make them, he goes into the science, mechanics, and history of food. When he talks about meringue, for instance, he explains why it is that getting even a tiny bit of yolk in with the whites will prevent the meringue from doing its thing. It's kind of a food version of Bill Nye the Science Guy.
In an episode we saw recently, Alton talked about meat pies. He told us that pie, a dish popular in the Middle Ages, comes from magpie. Magpies love to collect random crap and pile it up. A pie, during the middle ages, was a pile of crap. I mean not literally - it could include lots of different ingredients, like a magpie's nest might.
TV gets to say that sort of thing definitively, but it ain't necessarily so, according to the Online Etymology Dictionary. While the site does state that the pie/magpie link is possible, I suspect the word is probably more closely related to the middle Latin word pia, meaning pastry. In printers' slang (who knew printers had slang?), however, pie refers to a jumble of letters. This probably is a reference to the hoarding habits of magpies. 
Below the entries for pie, the site had an entry for piebald. Piebald is an adjective referring to a thing with two different colors, usually black and white. Bald in olden times could mean white (which explains why the bald eagle isn't actually bald); pie refers to the black color of the magpie. This term is usually applied to animals... for some reason, I had always thought the word was more commonly associated with people who have a premature white streak in their hair, like Stacy from What Not to Wear or Rogue from the X-Men (the idea that Rogue absorbed some of Magneto's hair, by the way, is a movie myth. Rogue has always rocked the skunk look). But apparently I was alone in that. Piebaldism in humans is a genetic disorder and usually involves discoloration of the face in addition to the hair.

Okay, you caught me. This isn't a magpie, it's a crow. Also, it's
not blurry on purpose, it's blurry because again, I had my
camera on the wrong setting. But it's still pretty cool.

The pied piper's name goes back to magpie too... pied, once upon a time, meant multicolored, in reference to the magpie being black and white. The pied piper might have been so called because he wore multicolored or motley clothing. Another theory says that the story of the pied piper might be an allegory for a plague - that a man whose skin was multicolored because of plague came into the actual historical town of Hamelin, and that plague carried the children off. But that's probably very fanciful and is perhaps a podcast for another day. 
"Shut your pie hole," according to The Word Detective, is derivative of the earlier British military slang cake hole. This doesn't have any fancy origins; it's just a colorful colloquialism.