Through his university research on Galician language, he became interested in etymology and the works of Manuel Rodrigues Lapa. This research, combined with his vast knowledge of the history of the Galician-Portuguese language led him re-interpret Galician classics and to develop the theory of what would become contemporary "reintegracionism": in short, the idea that had been stated in the past but never scientifically systematised that Galician and Portuguese languages were not just the same language in the past, sharing a common origin, but still are the same language today. Carballo Calero became the chief supporter of that view.