The Romans came into contact very early on with a group of Greek settlers known as the Graeci in southern Italy. By association the name was applied to all speakers of Greek, a very common occurrence. It's worth noting, however, that the words "Hellas" and "Hellenes" when used to refer to all Greek-speakers is rather late, and even in the Archaic Period there were a number of different names floating around that might describe the Greeks as a whole or various subsets of them. Homer's Hellenes, for example, only inhabit a small part of Phthia. Hesiod mentions Graecus, the eponymous ancestor of the Graeci (where they came from exactly is unclear), as being related to Hellen (not to be confused with Helen), the eponymous ancestor of the Hellenes. Aristotle placed the origin of the Hellenes up in Epirus and claimed that the name spread southward from there, although in reality it probably comes from closer to central Greece. How exactly it became to be used to describe all Greeks is very unclear, but in antiquity until well into the Roman Period Greek-speakers only identified themselves and others as Hellenes rather rarely. It's worth noting that the Roman province of what we would call Greece was the province of Achaea, also named by association with a particular region, though many of the cities of Greece were considered free cities and were therefore named in official documents and so forth individually, as they were not part of the province