Passage 2.3.8
Μήδεια δὲ τότε μὲν ἐλθοῦσα ἐς Ἀθήνας συνῴκησεν Αἰγεῖ, χρόνῳ δὲ ὕστερον φωραθεῖσα ἐπιβουλεύειν Θησεῖ καὶ ἐξ Ἀθηνῶν ἔφυγε, παραγενομένη δὲ ἐς τὴν λεγομένην τότε Ἀρίαν τοῖς ἀνθρώποις ἔδωκε τὸ ὄνομα καλεῖσθαι Μήδους ἀπʼ αὐτῆς· τὸν δὲ παῖδα, ὃν ἐπήγετο φεύγουσα ἐς τοὺς Ἀρίους, γενέσθαι λέγουσιν ἐξ Αἰγέως, ὄνομα δέ οἱ Μῆδον εἶναι· Ἑλλάνικος δὲ αὐτὸν Πολύξενον καλεῖ καὶ πατρὸς Ἰάσονός φησιν εἶναι.
Medea, arriving then at Athens, lived together with Aegeus; but later, after being discovered plotting against Theseus, she fled from Athens. Coming afterwards to the land then called Aria, she caused the inhabitants to adopt their name, Medes, after herself. The child whom she brought with her when escaping to the Arians is said to have been born to her from Aegeus, and his name was Medus. But Hellanicus calls him Polyxenus and claims that his father was Jason.