The English word "oregano" is a borrowing of the Spanish orégano, which derives from the Latin orīganum, which itself comes from Classical Greek ὀρίγανον (orī́ganon).

[12][13] The essential oil of oregano is composed primarily of monoterpenoids and monoterpenes, with the relative concentration of each compound varying widely across geographic origin and other factors.

A closely related plant is marjoram from Turkey, which differs significantly in taste because phenolic compounds are missing from its essential oil.

Factors such as climate, season, and soil composition may affect the aromatic oils present, and this effect may be greater than the differences between the various species of plants.

[20] Oregano is the staple herb of Italian cuisine, most frequently used with roasted, fried, or grilled vegetables, meat, and fish.

Its popularity in the U.S. began when soldiers returning from World War II brought back with them a taste for the "pizza herb", which had probably been eaten in Southern Italy for centuries.

During the summer, generous amounts of dried oregano are often added as a topping to a tomato and cucumber salad in Portugal, but it can be used to season meat and fish dishes as well.

In Spain, apart from seasoning, it is used in preparations of a variety of traditional dishes such as morcilla (Iberian pig blood sausage) and adobo sauce for fish and meat.

The dried and ground leaves are most often used in Greece to add flavour to Greek salad, and is usually added to the lemon-olive oil sauce that accompanies fish or meat grills and casseroles.

[17][22] In 2014, the U.S. Food and Drug Administration (FDA) warned a Utah company, Young Living, that its herbal products, including oregano essential oil, were being promoted to have numerous unproven anti-disease effects, and so were being sold as unauthorized misbranded drugs subject to seizure and federal penalties.

[23] Similar FDA warning letters for false advertising and unproven health claims about oregano essential oil products were published in 2017 and 2018.