Why is electrical wire called Romex?

Electrical wire is called Romex because Romex is the original brand name that became the genericized trademark for non-metallic sheathed cable, similar to how all facial tissues are often called Kleenex. The name was created by the Rome Wire Company in Rome, New York, in the 1920s. The company developed a new type of residential wiring that combined two or more rubber-insulated conductors wrapped in a woven fabric outer jacket with a rubberized inner layer, replacing the older knob-and-tube wiring that required separate wires and ceramic insulators. They named it ROMEX as a contraction of Rome plus EX for the experimental or extra features of the cable, and marketed it as a faster, cheaper, safer alternative for house wiring. The patent was granted and production expanded dramatically after World War II during the housing boom. In 1936, General Cable purchased Rome Wire, and later Southwire Company acquired the Romex trademark, which it still owns today and manufactures as Type NM-B. Because it was the first and most widely distributed product of its kind for decades, electricians and homeowners started calling any non-metallic sheathed cable Romex regardless of actual manufacturer, even though other brands like Cerro Wire and Encore produce the same NM-B cable. The term persists because it is shorter and more memorable than the technical designation NM-B.