Esso (ˈɛsoʊ) is a trading name for ExxonMobil. Originally, the name was primarily used by its predecessor Standard Oil of New Jersey after the breakup of the original Standard Oil company in 1911. The company adopted the name "Esso" (the phonetic pronunciation of Standard Oil's initials, 'S' and 'O'), to which the other Standard Oil companies would later object.
Standard Oil of New Jersey started marketing its products under the Esso brand in 1926. In 1972, the name Esso was largely replaced in the U.S. by the Exxon brand after the Standard Oil of New Jersey bought Humble Oil, while the Esso name remained widely used elsewhere. In most of the world, the Esso brand and the Mobil brand are the primary brand names of ExxonMobil, while the Exxon brand is used only in the United States alongside Mobil.
In 1911, Standard Oil was broken up into 34 companies, some of which were named Standard Oil and had the rights to that brand in certain states (the other companies had no territorial rights). The name Esso is the phonetic pronunciation of the initials 'S' and 'O' in the name Standard Oil. Standard Oil Company (New Jersey; "Jersey Standard") had the rights in that state, plus in Maryland, West Virginia, Virginia, North Carolina, South Carolina, and the District of Columbia. By 1941, it had also acquired the rights in Pennsylvania, Delaware, Arkansas, Tennessee, and Louisiana.
It also used the Esso brand in New York and the six New England states, where the Standard Oil Company of New York (Socony-Vacuum, later Socony Mobil) had the rights, but did not object to the New Jersey company's use of the trademark (the two companies did not merge until November 1999). However, in the other states, the other Standard Oil companies objected and, via a 1937 U.S. federal court injunction, forced Jersey Standard to use other brand names. In most states the company used the Enco ("Energy Company") brand name, and in a few, the Humble brand name.