Hispanic (Castilian Hispano, Portuguese Hispânico, Catalan: Hispà, from Latin Hispānus, adjective from Hispānia, the Roman name for the Iberian Peninsula) is a term that historically denoted relation to the ancient Hispania and its peoples.
Prior to the marriage of Queen Isabella of Castile and King Ferdinand of Aragon in 1469 the four Christian kingdoms of the Iberian Peninsula, Portugal, Aragon, Castile-Leon and Navarre were collectively referred to as Hispania. This usage, in medieval times, appears to have originated in provençal and appears to be first documented at the end of the XI Century. Indeed, in the Council of Constance the four kingsoms appear as if forming a single unity ("nación española") and all four shared one vote.
Though the term Hispania initially encompassed all of the Christian lands of Iberia, it was the union of Castile and Leon, Aragon and Navarre (only later to be formally known as the Kingdom of Spain) that would inherit the term.
The last time that the term Hispanic commonly included the Kingdom of Portugal was in 1640 prior to final Portuguese separation from the Habsburg kings then ruling the rest of Iberia in the period of the Iberian Union. From 1580 through 1640, the king of the kingdoms of Hispania used the title Rex Omniae Hispaniae, roughly translated "King of all the Hispanics." Thus, since at least the mid-17th Century, the term Hispanic has generally been used to refer to Spain, its people and its culture. Instead of Hispanic, Portugal adopted the word Lusitanic for the same purposes (in reference to the former Roman province of Lusitania, which was a part Hispania; ultimately, pertaining to the Lusitanians, one of the first Indo-European tribes to settle Europe). In this process, Portugal was excluded from the term..
With the expansion of the Spanish Empire, the peoples from Spain spread all over the world, creating new colonies and giving rise to the Hispanophone. This expansion was mainly concentrated in the Americas, especially in what is called Hispanic America, which comprises all those countries from the Americas that once belonged to the Spanish Empire and where the Spanish influence is still present (Brazil not being included since when it was settled by the Portuguese, the separation between the terms Hispanic pertaining to Spain and Lusitanic to Portugal was already effective). These countries, inherited the cultural and ancestral legacy of the Spaniards, and in consequence, their peoples and their cultures are also considered as Hispanic. Nowadays, the peoples from Hispanic America who live in the United States have developed their own identity with an unquestionable Hispanic substrate, and they are also considered Hispanics.