This paper focuses on Tapiete (Tupi-Guarani) and Vilela (Lule-Vilela), the two most severely endangered languages in the Argentine Chaco. Both show the results of linguistic attrition without obsolescence. However, the state of each one and chances for revitalization differ radically. While multigenerational Tapiete communities exist and are strengthening ties among themselves, the extreme paucity of Vilela speakers and the lack of a speech community have proven to be critical threats. The paper examines two particular aspects of language shift: borrowing in Tapiete and attrition in Vilela. Creative processes in the adaptation of loanwords have revealed linguistic resistance in Tapiete. In the case of Vilela, despite documented phonological and grammatical reduction, core linguistic structures have been activated through language remembering strategies. Although the pressure of Spanish has long been present, its structure has not been decisive to vernacular language loss. Rather, the abandonment of Tapiete and Vilela is rooted in the speakers' history of socio-cultural subordination.