How can I say the demonym of “Chaco”? In Spanish it is “chaqueño”, but I don’t know what the correct word is in English.
The only use of Chacoan I was able to find was in the English name of the charming little creature Cabassous chacoensis (Cabasú Chaqueño), the Chacoan naked-tailed armadillo, shown above. If in your writing you mention the Gran Chaco region several times, then use the word Chacoan, it will be understood as a demonym. Unless your English readers have a special thing for South American armadillos, however, it will not be a word they will likely have seen before.