and guanacos; that crowd is called chacu in the Quechua language, which is common in Peru, and that Spaniards have corrupted into Chaco".

However, the earliest known mention of the term in a document was in a letter written to Fernando Torres de Portugal y Mesía, Viceroy of Peru, dated in 1589, by the then Governor of Tucumán, Juan Ramírez de Velasco,