Passage 1.17.5
γῆς δὲ τῆς Θεσπρωτίδος ἔστι μέν που καὶ ἄλλα θέας ἄξια, ἱερόν τε Διὸς ἐν Δωδώνῃ καὶ ἱερὰ τοῦ θεοῦ φηγός· πρὸς δὲ τῇ Κιχύρῳ λίμνη τέ ἐστιν Ἀχερουσία καλουμένη καὶ ποταμὸς Ἀχέρων, ῥεῖ δὲ καὶ Κωκυτὸς ὕδωρ ἀτερπέστατον. Ὅμηρός τέ μοι δοκεῖ ταῦτα ἑωρακὼς ἔς τε τὴν ἄλλην ποίησιν ἀποτολμῆσαι τῶν ἐν Ἅιδου καὶ δὴ καὶ τὰ ὀνόματα τοῖς ποταμοῖς ἀπὸ τῶν ἐν Θεσπρωτίδι θέσθαι. τότε δὲ ἐχομένου Θησέως στρατεύουσιν ἐς Ἄφιδναν οἱ Τυνδάρεω παῖδες καὶ τήν τε Ἄφιδναν αἱροῦσι καὶ Μενεσθέα ἐπὶ βασιλείᾳ κατήγαγον·
In the land of Thesprotia there are indeed other sights worth seeing, notably the sanctuary of Zeus at Dodona and the sacred oak-tree of this god. Near Kichyros is a lake named Acherousia and the river Acheron; the Cocytus also flows there, a stream of most dismal water. Homer, I believe, having himself seen these places, ventured in his poetry to describe the underworld and even adopted the names of these rivers from those in Thesprotia. At that time, while Theseus was absent, the sons of Tyndareus marched against Aphidna, captured the town, and established Menestheus as king.