Ricotta is not a cheese but a creamy curd. The curd is literally cooked twice hence the name "ricotta," re-cooked. The leftover hot whey of milk used for cheese making has milk solids and a protein called albumin, which solidifies under high heat. When the whey is reheated (re-cooked) the solid milk parts are skimmed off to drain, and this is called ricotta cheese. Ricotta is known as an albumin or serum cheese, a cheese made as a by-product of provolone cheese from the recooked whey, hence its name. The foam of the whey when it is being recooked is called zabbina in Sicilian, which comes from the Arabic word zarb, thought also to be the root of the custard dessert zabaione. The best ricotta is made with sheep's milk.
Ricotta salata is a Sicilian specialty made from drained and dried ricotta. It is used in salads, grated over pasta and stuffed into some fritters.
The Greek antiquarian who wrote volumes on food, Athenaeus (c. A.D. 170-230), talks about "tender cheese" at a banquet. We don't know if this is ricotta, but he also mentions a cheese from Sicily that was well known. Ricotta cheese, which is generally recognized as having been invented in Sicily, is known in the language of the island by another name: zammatÓru, a word in Sicilian meaning "dairy farmer." This word is derived from the Arabic za'ama, meaning "cow," leading to the supposition that ricotta might have its origins in the Arab-Sicilian era.
Two of the earliest mentions or depictions of ricotta are related to Sicily. Professor Santi Correnti, chairman of the history department of the University of Catania and a preeminent historian of Sicily, writes that during the reign of the Sicilian king Frederick II, in the early thirteenth century, the king and his hunting party came across the hut of a dairy farmer making ricotta and, being ravenous, asked for some. Frederick pulled out his bread loaf, poured the hot ricotta and whey on top and advised his retinue that cu' non mancia ccu' so' cucchiaru lassa tutto 'o zammataru (Those who don't eat with a spoon will leave all their ricotta behind).
The first depiction of the making of ricotta is an illustration in the medical treatise known as the Tacuinum sanitatis (medieval health handbook), the Latin translation of the Arab physician Ibn Butlan's eleventh century Taqwim al-sihha.
Ortensio Lando in his Commentario delle piu notabili e mostruose cose d'Italia published in 1548 has his fictional traveler go to Val Calci, at some distance from Pisa, for the best ricotta in the world.