Anahuac, 1.5 miles above sea level between 19° and 20° north latitude and 98°45’ to 99°20’ west longitude, is the ancient core of Mexico. Anahuac is a Nahuatl name which means "close to water." It can be broken down like this: A(tl) + nahuac. Atl means 'water' and nahuac, which is a relational word that can be affixed to a noun, means "close to." Anahuac is sometimes used interchangeably with Valley of Mexico, but Anahuac properly designates the south-central part of the 8,000 km2 (3,000 mi2) Valley, where well-developed prehispanic culture traits had created distinctive landscapes now hidden by the urban sprawl of Mexico City. ("Valley of Mexico" is misnamed. It is a closed basin of internal drainage, not a valley.)
Anahuac (Aztec) Wikipedia
According to the 1911 Encyclopædia Britannica, Anahuac is "limited by the traditional and vaguely defined boundaries of an ancient American empire or confederation of that name previous to the Spanish conquest.
The word is said to signify 'country by the waters' in Nahuatl, the old Aztec language; hence the theory that Anahuac was located on the sea coast. One of the theories relating to the location of Anahuac describes it as all the plateau region of Mexico, with an area equal to three-fourths of the republic, and extending between the eastern and western coast ranges from Rio Grande to the isthmus of Tehuantepec. A more exact and more commonly used description, however, limits it to the great plateau valley in which the city of Mexico is located, between 18°40' and 20°30'N latitude, about 320 kilometers (200 mi) long by 120 kilometers (75 mi) wide, with an average elevation of 2300 meters (7500 feet), and a mean temperature of 17°C (62°F). The accepted meaning of the name fits this region as well as any on the sea coast, as the lakes of this valley formerly covered one-tenth of its area. The existence of the name in southern Utah, United States, and on the gulf coast of Mexico, has given rise to theories of other locations and wider bounds for the old Indian empire.Chisholm