This article is derived from a conference given online in the 2021 edition of Linguistweets – International Conference on Linguistics on Twitter, promoted by the Brazilian Association of Linguistics (Abralin). Our topic of debate is the Art of grammar of the most used language on the coast of Brazil (ANCHIETA, 1595), whose author is the missionary and humanist S. José de Anchieta, SJ (1534-1597). In the article, we divided our reflections on Anchieta's linguistic thought into three parts, analyzing, in the first two, external elements, related to the theoretical-cultural contextualization of his life and work, through the Historiography of Linguistics and Missionary Linguistics (ZWARTJES, 2011), in addition to Ecolinguistics, in an interdisciplinary perspective (COUTO, 2007). In the third part, we analyze internal elements in the description of linguistic facts of grammar and the linguistic thought of the missionary and humanist. For the internal analysis, we selected the sixth paragraph of the work, which is in the first chapter Das Letras (ANCHIETA, 1595, 1, 6).