The word Iberia is a noun adapted from the Latin word "Hiberia" originated by the Ancient Greek word Ἰβηρία (Ibēría) by Greek geographers under the rule of the Roman Empire to refer to what is known today in English as the Iberian Peninsula. At that time, the name did not describe a single political entity or a distinct population of people. Strabo's 'Iberia' was delineated from Keltikē (Gaul) by the Pyrenees and included the entire land mass southwest (he says "west") of there. The noun "Hiberia" fell into disuse when the Romans decided to call the most western part of the peninsula "Lusitania" (today Portugal) and the remaining territory "Hispania" (modern Spain). With the fall of the Roman Empire and the establishment of the new Castillian language in Spain, the word "Iberia" appeared for the first time in use as a direct 'descendant' of the Greek word "Ἰβηρία" and the Roman word "Hiberia".
The ancient Greeks reached the Iberian Peninsula, of which they had heard from the Phoenicians, by voyaging westward on the Mediterranean. Hecataeus of Miletus was the first known to use the term Iberia, which he wrote about circa 500 BC. Herodotus of Halicarnassus says of the Phocaeans that "it was they who made the Greeks acquainted with... Iberia." According to Strabo, prior historians used Iberia to mean the country "this side of the Ἶβηρος (Ibēros)" as far north as the river Rhône in France, but currently they set the Pyrenees as the limit. Polybius respects that limit, but identifies Iberia as the Mediterranean side as far south as Gibraltar, with the Atlantic side having no name. Elsewhere he says that Saguntum is "on the seaward foot of the range of hills connecting Iberia and Celtiberia."
According to Charles Ebel, the ancient sources in both Latin and Greek use Hispania and Hiberia (Greek: Iberia) as synonyms. The confusion of the words was because of an overlapping in political and geographic perspectives. The Latin word Hiberia, similar to the Greek Iberia, literally translates to "land of the Hiberians". This word was derived from the river Ebro, which the Romans called Hiberus. Hiber (Iberian) was thus used as a term for peoples living near the river Ebro. The first mention in Roman literature was by the annalist poet Ennius in 200 BC. Virgil refers to the Ipacatos Hiberos ("restless Iberi") in his Georgics. The Roman geographers and other prose writers from the time of the late Roman Republic called the entire peninsula Hispania.
As they became politically interested in the former Carthaginian territories, the Romans began to use the names Hispania Citerior and Hispania Ulterior for 'near' and 'far' Hispania. At the time Hispania was made up of three Roman provinces: Hispania Baetica, Hispania Tarraconensis, and Hispania Lusitania. Strabo says that the Romans use Hispania and Iberia synonymously, distinguishing between the near northern and the far southern provinces. (The name "Iberia" was ambiguous, being also the name of the Kingdom of Iberia in the Caucasus.)