The term that the ancient "
Greeks" used to describe the place they lived in.
Hellas includes the
Peloponnese and Greece North of the
Isthmus of Corinth. It would also have included islands of
Ionic Greeks near
Athens, but would not have considered to encompass the entire
Aegean to
Mytilene.
While the origin of this word is unknown (no, it's don't come from Hellen of Troy), it is known how the Hellenes came to be eroneously known as Greeks to modern societies. Sometime during the mid to late 4th century BC, when all of Hellas was under the yoke of Macedonian rule and the Romans were still just an ambitious people of the Italian Peninsula, a group of Romans came accross a group of Hellenes speaking a language they did not understand on the road near Hellas. Asked where they were from by the Romans (who communicated this idea in some unkown way), the Hellenes replied that they were from "Graia", an extremely insignifigant toilet of a city in the North of Hellas. The Romans, hearing this, refered to the speakers of the Hellenic language as "Graekes", later shortened to how we know them today.