the Indian name for a group of linguistically related tribes of the Uto-Aztecan group that lived in the territory of Mexico and some regions of Guatemala, Honduras, San Salvador, and Nicaragua before the Spanish conquest in the 16th century.
The Nahuatl had arrived from the north (from the southwestern regions of North America). Their migration had apparently taken place over the course of many centuries, beginning at about the turn of the Common Era. The Aztec were the last to enter the valley of Mexico (12th century). The Nahuatl were divided into two large subgroups: the Nahuat (the more ancient group), in Central America, and the Nahuatl (Tepanec, Acolhua, Chalca, Tlascaltec, Aztec) in Mexico. Some Nahuatl later lost their own languages and adopted Spanish; others merged into a single nationality speaking the Aztec language.
The conventional use of the term “Nahuatl” for the collective designation of the Indian tribes mentioned above and “Nahuatlan” for the designation of their language group has been adopted in modern scholarly literature.