Pesto is a paste that traditionally consists of crushed garlic, European pine nuts, coarse salt, basil leaves, and hard cheese such as Parmesan or pecorino sardo

Food 101

It originated in Genoa, the capital city of Liguria, Italy.The name pesto is the past participle of the Genoese verb pestâ (Italian: pestare), which means "to pound", "to crush", in reference to the original method of preparation. According to tradition, the ingredients are "crushed" or ground in a marble mortar through a circular motion of a wooden pestle. This same Latin root, through Old French, also gave rise to the English noun pestle