History of pie
Pie is often thought to be American in origin, as in "American Pie" but in actuality pie has a long history. In medieval England, "pyes" were usually savory - filled with beef, lamb, wild duck, magpie or pigeon — and spiced with pepper, currants or dates. However the Greeks are thought to have invented the pastry shell, made by combining water and flour. Meat pies were often part of Roman dessert courses (secundae mensea). Cato the Elder (234 – 149 BCE) gave a recipe for a cheesecake-like dish called 'placenta' in his treatise De Agricultura.
The purpose of a pie was to serve as a baking dish holding a savory filling. Pies were often baked in "coffins" a word that actually meant basket or box. Savory meat fillings were poured into a tall tin that had a sealable lid. Other pies were baked without a container and the pie shell itself was the container. These pies were called "traps". Pie shells often took the place of today's casserole dishes as their function was to contain the filling and the pastry was thick to allow long hours of cooking. Small pies are called tartlets and a large open-faced pie is called a tart.
Around 9,500 BC the Egyptians baked free-form pies called galettes. Ingredients used could include oat, wheat, rye and barley. Honey was used as a filling and the pie was baked over hot coals. 
Four and twenty blackbirds....
The English nursery rhyme Sing a Song of Sixpence, thought to date from in the 18th century, includes the lines "four and twenty blackbirds, baked in a pie/when the pie was opened the birds began to sing...".  In the Epulario (The Italian Banquet), by Giovanne De Rosselli, published in 1598, is a recipe for making a pie "That the Birds May Be Alive In them and Flie Out When It Is Cut Up." ("Make the coffin of a great pie or pastry, in the bottome thereof make a hole as big as your fist, or bigger if you will, let the sides of the coffin bee somwhat higher then ordinary pies, which done put it full of flower and bake it, and being baked, open the hole in the bottome, and take out the flower. Then having a pie of the bigness of the hole in the bottome of the coffin aforesaid, you shal put it into the coffin, withall put into the said coffin round about the aforesaid pie as many small live birds as the empty coffin will hold, besides the pie aforesaid. And this is to be at such time as you send the pie to the table, and set before the guests: where uncovering or cutting up the lid of the great pie, all the birds will flie out, which is to delight and pleasure shew to the company.")
- De Agricultura by Cato the Elder published in the Loeb Classical Library, 1934 The text is in the public domain.
- Pie, Lara Mayer Time Nov. 26, 2008
- Chambers Dictionary of Etymology
- [http://www.pbm.com/~lindahl/foc/ The Forme of Cury A Roll Of Ancient English Cookery, Compiled, about A.D. 1390, by the Master-Cooks of King Richard II,Presented afterwards to Queen Elizabeth, by Edward Lord Stafford
- Stradley, Linda. History of Pie. Retrieved on 2011-08-10.
- Sing a Song of Sixpence is listed in the Roud folk song index as number 13191.
- Rosselli, Giovanne De Epulario, or the Italian Banquet Wherein Is Shewed the Maner How to Dresse and Prepare All Kind of Flesh, Foules or Fishes. as Also How to Make Sauces, Tartes, Pies. with an Addition of Many Other Profitable and Necessary Things (1598) ISBN 9781171324461