The ethnic names, still in use in 1940, to designate the indigenous peoples of the Chaco Boreal (Chulupi, Moro, Chamacoco, Lenguas. . . ) were gradually replaced over the following decades by a new layer of names (Nivaclé, Ayoreo, Ishir, Enlhet. . . ) all of which can be translated as « men », or « humans ». Is this simply a semantic evolution or a more profound transformation in the social and historical agency of these groups? Does the advent of an anthroponym as an ethnic name confirm the ethnocentric character of these societies or is it more likely a result of the dismantling of inter-ethnic relations and ultimately of the occupation and colonization of the Chaco after the Paraguayan-Bolivian war? Based on work by different authors, this article analyzes the different ethnonymic strata in the northern Chaco beginning with the most recent ones and reaching back to those from the colonial era. As a result, the Chaco - which 18th century Jesuits called the « American Babel » because of its unstable linguistic fragmentation - will become more intelligible.