Discussion of accentuation rules for simple adjectives and verbs ending in -τος and -στος, and of place-names/ethnics formed with these endings (examples: Αἴγυπτος, Λύκαστος, Ὀγχηστός); citations from Homer, Herodotus, Pausanias, etc.
Τὰ εἰς 'τος' ἁπλᾶ ὑπὲρ δύο συλλαβὰς ἔχοντα πρὸ τοῦ 'τ' ψιλὸν κατ´ ἐπιπλοκὴν ἐπιθετικὰ ὄντα καὶ ῥηματικὰ ὀξύνεται, ἑλικτός, ἀμελκτός, χαρακτός, ὀρεκτός. τὸ μέντοι Αἴγυπτος—ἡ χώρα καὶ ὁ ποταμός. ἐκλήθη ἀπὸ τοῦ Αἰγύπτου, ὡς Χάραξ «Βήλου παῖς ὢν καὶ Ἀερίας τῆς καὶ Ποταμίτιδος βασιλεύσας ἔτη τριάκοντα τρία». —καὶ Πάνακτος καὶ Ναύπακτος πόλις Αἰτωλίας ἀπὸ ναυπηγίας τῶν Ἡρακλειδῶν, ὡς Ἔφορος καὶ Στράβων. καὶ Πρόνεκτος πόλις Βιθυνίας καὶ Δατύλεπτος ἔθνος Θρᾴκης. Ἑκαταῖος Εὐρώπῃ—μὴ ὄντα ῥηματικὰ προπαροξύνεται. σεσημείωται τὸ δρυφακτός ὀξυνόμενον, ἡ θύρα τοῦ δικαστηρίου, ἣ καὶ κιγκλίδες καλοῦνται. Τὰ εἰς 'στος' κύρια ἀρσενικὰ μόνως ἢ θηλυκὰ βαρύνεται, Ἄκαστος. Λύκαστος πόλις Κρήτης. Ὅμηρος «Λύκτον Μίλητόν τε καὶ ἀργινόεντα Λύκαστον» (Β 647) ἀπὸ Λυκάστου αὐτόχθονος ἢ παιδὸς τοῦ Μίνωος. ἔστι καὶ Ποντικὴ Λύκαστος. τὴν Κρητικὴν Λύκαστον ὀξύνουσιν οἱ ἐγχώριοι, ὡς ἱστορεῖ Διονύσιος. οὐκ ἐπικρατεῖ δὲ ἡ ἐθνικὴ παράδοσις. Ἥφαιστος. Ἄδραστος βασιλεύς, ἀφ´ οὗ πόλις Ἀδράστεια. Βίβαστος Θρᾴκης πόλις. Βούβαστος πόλις Αἰγύπτου, ἣν Ἡρόδοτος (e. g. 2, 59) Βούβαστίν φησι διὰ τοῦ 'ι'. Μούμαστος πόλις Καρίας. Ἀλέξανδρος δευτέρῳ Καρικῶν. Ἔγεστος ὁ Τρωός, ἀφ´ οὗ Ἔγεστα πόλις Σικελίας. Αἴγεστος στρατηγός τις, ἀφ´ οὗ Αἰγεσταῖοι οἱ Θεσπρωτοί. Πραίνεστος πόλις Ἰταλίας ἀπὸ Πραινέστου τοῦ Λατίνου τοῦ Ὀδυσσέως καὶ Κίρκης υἱοῦ. Μάκιστος ὁ ἀδελφὸς Φρίξου καὶ πόλις τῆς Τριφυλίας. Ἀνάφλυστος δῆμος τῆς Ἀντιοχίδος φυλῆς ἀπὸ Ἀναφλύστου ἥρωος. Παυσανίας δευτέρῳ ( 30, 9) «Τροιζῆνος οἱ παῖδες Ἀνάφλυστος καὶ Σφῆττος». Κάρυστος ὁ Χείρωνος καὶ ἀπ´ αὐτοῦ πόλις ὑπὸ τῇ Ὄχῃ ὄρει τῆς Εὐβοίας. ἔστι καὶ Κάρυστος τόπος τῆς Αἴγυος πρὸς Ἀρκαδίαν, ἀφ´ οὗ Καρύστιον οἶνον Ἀλκμὰν ἔφη, καθὰ Στράβων δεκάτῃ. τὰ δὲ προσηγορικὰ ὀξύνεται, ἀγοστός ἡ ἀγκάλη, ὀϊστός. * Τὰ εἰς 'στος' τῷ 'η' παραληγόμενα κύρια ὀξύνεται, Ὀγχηστός ἄλσος. Ὅμηρος «Ὀγχηστόν θ´ ἱερόν, Ποσιδήϊον ἀγλαὸν ἄλσος» (Β 506). —ἱδρυνθὲν ὑπὸ Ὀγχηστοῦ τοῦ Βοιωτοῦ, ὥς φησιν Ἡσίοδος. ἔστι καὶ πόλις, ὡς Παυσανίας ἐνάτῳ ( 26, 6). Ἀπολλώνιος δὲ ὁ Ῥόδιος.... πόλιν φησὶ μεγάλην τὸν Ὀγχηστὸν μεταξὺ Ἁλιαρτίων καὶ Ἀκραιφνίων. Τυφρηστός πόλις τῆς Τραχῖνος ὀνομασθεῖσα ἀπὸ τῆς τέφρας Ἡρακλέους ἢ ἀπὸ Τυφρηστοῦ υἱοῦ Σπερχειοῦ. Τὰ εἰς 'στος' ἐπιθετικὰ ἁπλᾶ ῥηματικὰ ὑπὲρ δύο συλλαβὰς ὀξύνεται,
Simple words in -τος, of more than two syllables, having a smooth breathing before the τ, when by composition they are adjectival and verbal, are accented on the last syllable: ἑλικτός, ἀμελκτός, χαρακτός, ὀρεκτός. But Αἴγυπτος—the country and the river—was so called from Αἴγυπτος, as Charax [says]: “Belus’ son, and having reigned over Aeria, also called Potamititis, for thirty-three years.” And Πάνακτος and Ναύπακτος, a city of Aetolia, from the shipbuilding of the Heraclids, as Ephorus and Strabo [say]. And Πρόνεκτος, a city of Bithynia, and Δατύλεπτος, a people of Thrace. Hecataeus in his Europa [notes that such forms], not being verbal, are accented on the antepenult. Marked as an exception is δρυφακτός, accented on the last syllable: the door of the court, which is also called κιγκλίδες. Proper names in -στος, masculine only or feminine, are accented with a grave: Ἄκαστος. Λύκαστος, a city of Crete. Homer: “Λύκτον Μίλητόν τε καὶ ἀργινόεντα Λύκαστον” (Β 647), from Lycastus, an autochthon, or a son of Minos. There is also a Pontic Λύκαστος. The locals accent the Cretan Λύκαστος on the last syllable, as Dionysius relates; but the local tradition does not prevail. Ἥφαιστος. Ἄδραστος, a king, from whom the city Ἀδράστεια [is named]. Βίβαστος, a city of Thrace. Βούβαστος, a city of Egypt, which Herodotus (e. g. 2, 59) says is Βούβαστιν with ι. Μούμαστος, a city of Caria. Alexander in the second [book] of his Carica. Ἔγεστος the Trojan, from whom Ἔγεστα, a city of Sicily. Αἴγεστος, a certain general, from whom the Thesprotians are called Αἰγεσταῖοι. Πραίνεστος, a city of Italy, from Praenestus the Latin, son of Odysseus and Circe. Μάκιστος, the brother of Phrixus, and a city of Triphylia. Ἀνάφλυστος, a deme of the tribe Antiochis, from the hero Ἀνάφλυστος. Pausanias in the second (30, 9): “The sons of Troezen: Ἀνάφλυστος and Σφῆττος.” Κάρυστος, [son] of Cheiron, and from him a city under Mount Oche in Euboea. There is also Κάρυστος, a place of Aegys toward Arcadia, from which Alcman spoke of Καρύστιον wine, as Strabo [says] in the tenth [book]. But appellatives are accented on the last syllable: ἀγοστός, ‘the armful’, ὀϊστός. Proper names in -στος with η in the penult are accented on the last syllable: Ὀγχηστός, a grove. Homer: “Ὀγχηστὸν θ᾽ ἱερόν, Ποσιδήϊον ἀγλαὸν ἄλσος” (Β 506)—founded by Ὀγχηστός the Boeotian, as Hesiod says. There is also a city, as Pausanias [says] in the ninth (26, 6). Apollonius Rhodius … says that Ὀγχηστός is a great city between Haliartians and Acraephnians. Τυφρηστός, a city of Trachis, named either from the ashes of Heracles or from Τυφρηστός, son of Spercheius. Simple verbal adjectives in -στος, of more than two syllables, are accented on the last syllable.