Passage 8.18.2
Ἐπιμενίδης δὲ ὁ Κρὴς εἶναι μὲν καὶ οὗτος θυγατέρα Ὠκεανοῦ τὴν Στύγα ἐποίησε, συνοικεῖν δὲ αὐτὴν οὐ Πάλλαντι, ἀλλὰ ἐκ Πείραντος Ἔχιδναν τεκεῖν, ὅστις δὴ ὁ Πείρας ἐστί. μάλιστα δὲ τῆς Στυγὸς τὸ ὄνομα ἐς τὴν ποίησιν ἐπεισηγάγετο Ὅμηρος. ἐν μέν γε Ἥρας ἐποίησεν ὅρκῳ ἴστω νῦν τόδε γαῖα καὶ οὐρανὸς εὐρὺς ὕπερθεν καὶ τὸ κατειβόμενον Στυγὸς ὕδωρ· Hom. Il. 15.36-37 ταῦτα μὲν δὴ ἐποίησεν ὡς ἂν ἰδὼν ἐς τὸ ὕδωρ τῆς Στυγὸς στάζον· βούλεται δὲ καὶ ἐν καταλόγῳ τῶν μετὰ Γουνέως Τιταρησίῳ ποταμῷ ῥεῖν τὸ ὕδωρ ἀπὸ τῆς Στυγός.
Epimenides the Cretan, indeed, also made Styx a daughter of Oceanus, but did not represent her as living with Pallas; rather, she bore Echidna from Peiras, whoever this Peiras may be. Homer was especially responsible for introducing the name of Styx into poetry, for it is in Hera's oath that he composed: "Now let this be witnessed by Earth and broad Heaven above, and the down-flowing water of Styx." Indeed, Homer wrote these lines as if he had seen the dripping water of Styx; and in the Catalogue [of Ships] he also wishes the water of Styx to flow as the river Titaresios, a tributary of the Peneios, near Guneus.