Arcadian Greek language
Arcadians were purely Achaeans, the first Indo-European inhabitants of Greece. Linguists believe it is Arcadian ethnic group that was the descendant of ancient Achaean civilization which flourished until the 12th century in Peloponnese with the main cities of Mycenae, Tyrinth, Argos and others. After the Doric tribes invaded Greece in the 12th century, Achaeans were partly eliminated, partly assimilated by Doric settlers, and remained only in Attic region, on some Aegean islands and here in Arcadia.

That is why Arcadian is quite archaic, but more developed and less "barbarian" than Doric. The Arcadian language also includes Cypriot (on Cyprus island) and Pamphilian (in the southern region of Asia Minor) dialects, which were developed later by migrants, in the epoch of Great Colonization.

One of the interesting features of Arcadian is the form of genitive singular of nouns which had -au ending unique among Greek dialects.