The derivation of the word may be from magpie, shortened to pie.
The explanation offered in favour or this is that the magpie collects a variety of things, and that it was an essential feature of early pies that they contained a variety of ingredients." ---The Oxford Companion to Food, Alan Davidson, 2nd edition, Tom Jaine editor [Oxford University Press: Oxford] 2006 (p.
Modern pie, as we Americans know it today, descends from Medieval European ingredients (fat=suet, lard, butter) and technology (pie plates, freestanding pies, tiny tarts).
"The idea of enclosing meat inside a sort of pastry made from flour and oil originated in ancient Rome, but it was the northern European use of lard and butter to make a pastry shell that could be rolled out and moulded that led to the advent of true pie." ---An A-Z of Food & Drink, John Ayto [Oxford University Press: Oxford] 2002 (p.
Remove the skin and make diagonal incisions into the meat. Then make a dough of oil and flour and wrap the ham in it. "Cover the base of a pan, large enough to take the ham, with figs and lay the ham, stuffed with figs, on top. Cover, and boil the ham for 1 hour over a low heat. When the ham is cooked, dry it well and make incisions all over the flesh. Rub the fat into the flour until it resembles breadcrumbs. Different inventories list different ingredients for mersu, so there were many recipes. Finished product wraps dough around filling, free form, not in a pie dish.] Medieval European pies There is some controversy whether the pastry crust used in Medieval times was meant for eating or as a cooking receptacle. A careful examination of these early recipes reveals crust purpose.
 Experimenting with this formula, we have adhered to the instructions as closely as possible, using regular pie dough to envelope the parboiled meat.A piecrust used less flour than bread and did not require anything as complicated as a brick oven for baking.More important, though, was how pies could stretch even the most meager provisions into sustaining a few more hungry mouths...603) First pies Food historians confirm ancient people made pastry.Recipes, cooking techniques, meal presence and presentations varied according to culture and cuisine.
Some pie-type foods are made for individual consumption. pasties, turnovers, empanadas, pierogi, calzones..enjoyed by working classes and sold by street vendors.