“Aztlán” (from Astlan, ˈast͡ɬãːn̥) is the ancestral home of the Aztec peoples. Astekah is the Nahuatl word for "people from Aztlan". Aztlan is mentioned in several ethnohistorical sources dating from the colonial period, and while they each cite varying lists of the different tribal groups who participated in the migration from Aztlan to central Mexico, the Mexica who went on to found Mexico-Tenochtitlan are mentioned in all of the accounts.
Historians have speculated about the possible location of Aztlan and tend to place it either in northwestern Mexico or the Southwestern United States, although there are doubts about whether the place is purely mythical or represents a historical reality.
Nahuatl histories relate that seven tribes lived in Chicomoztoc, or "the place of the seven caves". Each cave represented a different Nahua group: the Xochimilca, Tlahuica, Acolhua, Tlaxcalteca, Tepaneca, Chalca, and Mexica. Along with these people, the Olmec-Xicalanca and Xaltocamecas are also said to come from Aztlan. Because of their common linguistic origin, those groups are called collectively "Nahualteca" (Nahua people). These tribes subsequently left the caves and settled "near" Aztlán.
The various descriptions of Aztlán apparently contradict each other. While some legends describe Aztlán as a paradise, the Codex Aubin says that the Aztecs were subject to a tyrannical elite called the Azteca Chicomoztoca. Guided by their priest, the Aztec tribe fled. On the road, their god Huitzilopochtli forbade them to call themselves Azteca, telling them that they should be known as Mexica. Scholars of the 19th century—in particular Alexander von Humboldt and William H. Prescott—translated the word Azteca, as is shown in the Aubin Codex, to Aztec.
Some say that the southward migration began on May 24, 1064, CE, after the Crab Nebula events from May to July 1054. Each of the seven groups is credited with founding a different major city-state in Central Mexico.