Orseis

In Greek mythology, Orseïs (; Ancient Greek: Ὀρσηΐς, derived from ὄρσω - "orsô", "to rouse, stir, awaken, excite or arise") was the water-nymph (Naiad) of a spring in Thessalia, Greece, and the mythical ancestor of the Greeks. In some accounts, she was described as a mountain nymph (oread) of Mt. Othrys and named as Othryis. 
Mythology.
It is uncertain whether Orseis was believed to be the daughter of Oceanus or the river-god of Thessalia, Peneios. There is even a possibility that she was the daughter of Zeus and Deino the Graeae. 
According to the "Library", Orseis married Hellen, son of Deucalion and Pyrrha and brother of Pandora, the legendary eponymous ancestor of the Greeks. Their sons, Dorus, Xuthus, and Aeolus, according to Hesiod's "Eoiae" or "Catalogue of Women" together with the sons of Pandora, Graecus, Magnetas and Makedon with Zeus, became the founders of the seven primordial tribes of Hellas (Graecians, Magnetes, Makedones, Dorians, Achaeans, Ionians, and Aeolians). In some accounts, Xenopatra was also called the daughter of Hellen and Orseis.