Which is it? Calormen or Calormene?

According to the books, "Calormen" is a country. "Calormene" indicates nationality/place of origin. Therefore a character is a Calormene from Calormen, like Tumnus is a Narnian from Narnia. CoN Reference: Horse and His Boy, Chapter 4, Paragraph 24 (other examples exist, but this is the most illustrative)