Pizza is a snack that comes to us straight from the Neolithic. It's a direct descendant of the kind of bread people made before there were ovens.
Focaccia, the Italian name for the bread pizza is made with, comes from the Latin word for hearth. The original way of making it was simple. You built a fire on a flat rock--or in your fireplace, if you had one--and when the hearth was good and hot, you brushed away the coals and laid a thin sheet of dough on the stone until it was done.
In time, people realized that the bread cooked better if they inverted a pot over it to hold in the heat. Eventually somebody attached a clay dome to the hearth stone and the oven was invented. But many people cooked on the hearth right down to modern times, simply because they couldn't afford ovens.
People have always liked to add a little variety to the staff of life by sprinkling their bread with seeds, spices, onions and the like. The temptation is particularly great with something like focaccia, which practically begs for something to adorn its big, flat surface. In Egypt, this tradition goes back to the days of the pharaohs, and in medieval Cairo there was even a law that required every loaf of bread to be sprinkled with seeds or spices.
Sometimes the toppings are more substantial, making something we might call a pizza. In northeastern Spain, they make coca, a sort of pizza topped with honey and almonds. On the French Riviera, pissaladiere has a layer of olives and anchovies (which are called pissala-- they, and not the word pizza , give pissaladiere its name). In Syria and Armenia, there is a sort of ground lamb pizza called lahm bi-ajin (lahmajun).
The Italian pizza we know today, with its layers of tomatoes, cheese and other toppings, is by far the most elaborate of them. But in this form it is not an age-old dish. For the first 12 or 13 centuries of its history, pizza was just a word for the ancient hearth bread or various flat oven breads descended from it.
The reason it wasn't simply called focaccia is that in the Middle Ages, Southern Italy was part of the Byzantine Empire, and the dominant language there was Greek, not Italian. The original Greek word for a flat bread had been plakous, but shortly before the Byzantine conquest of Italy, plakous came to mean a sort of cake or spice bread. Since the Greeks still made thin, flat bread, they needed a new word for it, and the word they chose was pitta.
Pitta was the Athenian word for "pitch," and the reasoning was probably that the pitch that comes from trees forms flat layers or cakes. It might not seem the most obvious word to choose--you probably had to be there. It worked well enough, anyway, and even today pitta means a flat bread in Greek. (Ironically, though, like plakous it has also come to mean a sort of cake, as in the modern Greek pastries spanakopitta and tyropitta.)
With the meanings "layer" and "flat bread," the word had already spread through the Balkans by the 6th Century. In Albania, pete means noodle or strudel dough. In Friuli, the far northeastern corner of Italy, pete is a sort of coffee cake with raisins and figs. It was probably through Romanian that Modern Hebrew got the word pita, the famous Israeli name for the flat Near Eastern pocket bread.
In Italy, to judge by the way the word pitta is used by the few people in Calabria and Basilicata who still speak Greek, it meant either a flat bread or dough rolled out thin as for noodles. North of the provinces where Greek lingers on, pitta became pizza and spread up through a large part of Italy.
Basically it meant a flat bread. There were a lot of variations (in Abruzzo and Molise, there is a pizza made of cornmeal), and often pizza was sweetened. A 17th Century Italian-English dictionary defined pizza as "a sort of rugged cake, simnell-bread (a bread containing currants and almonds) or wafer. Also a kind of sugar tart." Sweet pizza is still common in Northern Italy, particularly at Christmas.
The pizza that conquered the world, though, was the pizza of Naples. It was originally a rough laborers' snack that might or might not have a topping. Then in 1889, a Neapolitan baker named Raffaele Esposito made the first pizza with a cheese topping as we know it. To celebrate the colors of the Italian flag--red, yellow and green--he created a pizza topped with a new combination of tomatoes, mozzarella and basil.
He named it patriotically after the Queen of Italy, Margherita Teresa Giovanni. It was the classic "cheese pizza," and it made not only cheese but tomato an essential ingredient in pizza, at least in Naples. Nearly every pizza invented since has been based on pizza Margherita, and there have been a lot of them, particularly since the invention of the "deep dish" pizza (at Pizzeria Uno in Chicago in the early '40s) and the pizza-mania of California restaurants in the last decade.
The first pizza bakery in this country opened 86 years ago in New York. Pizza first became widely popular in the early '50s, but due to the latest explosion in popularity, there are now more than 53,000 pizzerias in the United States and pizza has become part of the American mainstream. It's the favorite food of children between ages 3 and 11, and 28% of the cheese made in this country today is mozzarella, mostly for pizza.
It's simple. Take a Neolithic bread, add tomatoes, mozzarella and pepperoni, and you've got a hit on your hands.