Nachos are not named for an ingredient or a region. They are named for one man, using his nickname. Nacho is the usual Spanish short form of Ignacio.
Ignacio Anaya worked at the Victory Club, a restaurant in Piedras Negras, in the Mexican state of Coahuila. The town sits across the Rio Grande from Eagle Pass, Texas. Across the river was Fort Duncan, a U.S. military post.
The story, as Wikipedia tells it, is set in 1943. A group of American officers' wives came over the border to eat, among them a woman named Mamie Finan. The cook could not be found. Anaya went into the kitchen and put together something from what was there.
He cut fried tortillas into triangles, topped them with shredded Colby cheese and slices of pickled jalapeño, and heated them. Asked what the dish was called, he answered that they could call it Nacho's Special. Etymonline gives the Spanish form as Nachos Especial.
The details wobble a little depending on the source. Etymonline calls Anaya a bartender and dates the invention to about 1941. It also cites a 1964 interview in the Houston Post. There, Anaya said the dish was a variant of the quesadilla, made on a tortilla cut into quarters rather than on chips. The core of the story does not change: the dish is named for Anaya.
The word reached English print early. Wikipedia gives 1949, in the book A Taste of Texas. Anaya's recipe appeared in the St. Anne's Cookbook in 1954. He later opened his own place in Piedras Negras, Nacho's Restaurant, and died in 1975. The town put up a bronze plaque in his honor, and October 21 became the International Day of the Nacho.
The version most Americans know came later. In 1976 Frank Liberto sold nachos with a pumpable cheese sauce at Arlington Stadium, during Texas Rangers games. Sportscaster Howard Cosell then talked them up on Monday Night Football in September 1978. That turned a border-town improvisation into a stadium staple.