Names given to the Spanish language

There are two names given in Spanish to the Spanish language: español ("Spanish") and castellano ("Castilian"). Spanish speakers from different countries or backgrounds can show a preference for one term or the other, or use them indiscriminately, but political issues or common usage might lead speakers to prefer one term over the other. This article identifies the differences between those terms, the countries or backgrounds that show a preference for one or the other, and the implications the choice of words might have for a native Spanish speaker.

Generally speaking, both terms can refer to the Spanish language as a whole, with a preference for one over the other that depends on the context or the speaker's origin. Castellano (as well as Castilian in English) has another, more restricted, meaning, relating either to the old Romance language spoken in the Kingdom of Castile in the Middle Ages, predecessor of the modern Spanish language, or to the variety of Spanish nowadays spoken in the historical region of Castile, in central Spain.

Originally Castilian (castellano) referred to the language of the Kingdom of Castile, one of several northern kingdoms that spread across the Iberian Peninsula through the Middle Ages, from about the 8th to the 15th centuries. Traditionally the first recorded examples of written Castilian/Spanish are considered to be the Glosas Emilianenses, a number of isolated words added to a Latin text as an aid to the reader, dated to the eleventh century. Soon after that there begin to appear discursive texts in Castilian, such as the Cantar de Mio Cid. This early Romance language was derived from Latin and evolved into modern Spanish.

However, the term Spanish (español) is a more recent term that first referred to Spain as a country, and then to the predominant language spoken in that country. Spain as a truly unified nation appeared centuries later than the language and the Kingdom of Castile; in fact, it was only in the late 15th century that the personal union between the Crowns of Castile and Aragon unified Spain. The actual legal unification date is disputed, but commonly agreed to have occurred not earlier than the eighteenth century. Only then did the Castilian language begin to be commonly called Spanish.

...
Wikipedia