In ancient Rome, panis focacius was a flat bread baked on the hearth. The word is derived from the Latin focus meaning “hearth, place for baking.” The basic recipe is thought by some to have originated with the Etruscans or ancient Greeks, but today it is widely associated with Ligurian cuisine.
As the tradition spread, the different dialects and diverse local ingredients resulted in a large variety of bread (some may even be considered cake). Due to the number of small towns and hamlets dotting the coast of Liguria, the focaccia recipe has fragmented into countless variations (from the biscuit-hard focaccia of Camogli to the oily softness of the one made in Voltri), with some bearing little resemblance to its original form. The most extreme example is the specialty “focaccia col formaggio” (focaccia with cheese) which is made in Recco, near Genoa. Other than the name, this Recco version bears no resemblance to other focaccia varieties, having a caillé and cheese filling sandwiched between two layers of paper-thin dough. It is even being considered for European Union PGI status. Regional variations also exist, such as focaccia dolce (sweet focaccia), popular in some parts of north-western Italy, consisting of a basic focaccia base and sprinkled lightly with sugar, or including raisins, honey, or other sweet ingredients.
Focaccia is present in many variants in Italy itself, for example the focaccia alla genovese, originated in Genoa, the focaccia alla barese, from Bari, or the focaccia alla messinese, from Messina. Another widespread variation is the Focaccia Barese, common in the provinces of Bari, Brindisi, Lecce and Taranto. It usually comes in three variations: classic focaccia with fresh tomatoes and olives, potato focaccia with potato slices 5 mm thick and white Focaccia with salt grains and rosemary. Some other variations include peppers, onions, eggplant or other vegetables.
In Burgundy, focaccia is called “foisse” or “fouaisse”, and in Catalonia, Provence and Languedoc it’s “fogassa” or, more commonly, the French “fougasse“. In Argentina, it is widely consumed under the name fugazza, derived from fugàssa in the native language of Argentina’s many Ligurian immigrants. The Spaniards call it “hogaza”.
In American-English, it is sometimes referred to as focaccia bread. The Sicilian-style pizza, and the Roman pizza bianca (white pizza) can be considered a variant of focaccia. Focaccia is used extensively as a sandwich bread outside of Italy.
*info taken from Wikipedia UK