Resumen: This paper focuses on Navarre, a small kingdom near the French border, which was independent during the Middle Ages. The original language of Navarre was Basque, a non-Romance language, which was also unwritten, as the political powers used Latin, Navarrese Romance, French, Occitan or other languages. In 1512 Navarre was conquered by the Catholic king, Ferdinand, and incorporated into Castile as part of the Spanish kingdom. After the union the Navarrese elite tried to adapt to their new situation by learning Spanish; this was also a way of gaining access to overseas trade. There were cultural as well as linguistic differences between Navarre and Castile for example in the conception of a woman¿s role in the household and in the transmission of property from one generation to the next. Rules governing inheritance also affected the transmission of family names. The result of the incorporation of Navarre into Castile was a peculiar anthroponomastic system, a mixture of both cultures.