Lunfardo was first described in Argentina at the end of the 19th century as the jargon of thieves of Buenos Aires, themselves called lunfardos. The current definition of the term, though, focuses on the immigratory milieu of Argentina in which this linguistic repertoire was formed, and considers the connection to criminality as but one of its features. This study analyzes six of the earliest sources depicting Lunfardo as criminal jargon and places them in the socio-historical and intellectual context of Buenos Aires and Argentina between the 1880s and the 1910s. The purpose of this study is to understand the discourse within which that original exclusive connection to criminality was made and came to dominate the understanding of Lunfardo until the 1950s. As those were the years of the consolidation of the national identity of Argentina, this paper aims to provide new insights on an important moment in the process of the Argentine national formation.