Chichimeca (tʃitʃiˈmeka) is the name that the Nahua peoples of Mexico generically applied to nomadic and semi-nomadic peoples who were established in present-day Bajío region of Mexico. Chichimeca carried the meaning as the Roman term "barbarian" that described Germanic tribes. The name, with its pejorative sense, was adopted by the Spanish Empire. In the words of scholar Charlotte M. Gradie, "for the Spanish, the Chichimecas were a wild, nomadic people who lived north of the Valley of Mexico. They had no fixed dwelling places, lived by hunting, wore little clothes and fiercely resisted foreign intrusion into their territory, which happened to contain silver mines the Spanish wished to exploit." Gradie noted that Chichimeca was used as a broad and generalizing term by outsiders, writing, "[it] was used by both Spanish and Nahuatl speakers to refer collectively to many different people who exhibited a wide range of cultural development from hunter-gatherers to sedentary agriculturalists with sophisticated political organizations." They practiced animal sacrifice, and they were feared for their expertise and brutality in war.
The Chichimeca War (1550-1590) ended with the Spanish making favorable peace terms with the Chichimeca. Spanish/Chichimeca interaction resulted in a "drastic population decline in population of all the peoples known collectively as Chichimecas, and to their eventual disappearance as peoples of all save the Pames of San Luis Potosí and the related Chichimeca-Jonaz of the Sierra Gorda in eastern Guanajuato." In modern times, only one ethnic group is customarily referred to as Chichimecs, namely the Chichimeca Jonaz, a few thousand of whom live in the state of Guanajuato.
The Nahuatl name Chīchīmēcah (plural, pronounced tʃiːtʃiːˈmeːkaʔ; singular Chīchīmēcatl) means "inhabitants of Chichiman," Chichiman meaning "area of milk." It is sometimes said to be related to chichi "dog", but both i'''s in chichi are short, and both in Chīchīmēcah are long. That changes the meaning, as vowel length is phonemic in Nahuatl.