This chapter critically reevaluates the role of structural change in the development of the concept of Língua Geral, as proposed in Rodrigues (1986,1996, 2010; see also EDELWEISS, 1947, 1969; DIETRICH, 2014). In Rodrigues’s model, two languages, Língua Geral Paulista and Língua Geral Amazônica, emerged from the Tupi and Tupinambá languages spoken by bi- or multilingual ‘Mamluks’ (Luso-Amerindian mestizos) over the 16th and 17th centuries. However, a socio-philological analysis (WRIGHT, 1982, 1991, 1994, 2002) applied to a broad sample of Luso-Brazilian colonial sources, reveals that contemporaries neither attributed a characteristic variety of Língua Geral to the mamluks nor classified Língua Geral diatopically . Moreover, in 18th c. Amazonia, the linguistically non-Tupi-Guarani Tapuia peoples, rather than the Mamluks, were explicitly identified as agents of linguistic change (Daniel, 2004 [1757-1776]); however, no new name emerged. Thus, although language contact and shift undeniably occurred and undoubtedly contributed to structural change, Rodrigues’ hypothesis regarding the Mamluks’ central role in the formation of the Língua Geral cannot be sustained. We therefore develop a revised trajectory for Língua Geral in which we propose that perceived changes in function rather than observed structural divergence were responsible the shift from using ‘Língua Brasílica’ in 17th c. Jesuit publications to ‘Língua Geral ‘in the 18th c. Our research highlights the need for a re-assessment of the term Língua Geral, and, in particular, the anachronistic Ausbau of periodizations and varieties on the basis of later perceived structural Abstand (KLOSS, 1967, 1976, 1978) that do not correspond to contemporary usage.