Schol. to Pin. Nemian Odes, 4.81
“Phylarkhos claims that Thetis went to Hephaistos on Olympos so that he might create weapons for Achilles and that he did it. But, because Hephaistos was lusting after Thetis, he said he would not give them to her unless she had sex with him. She promised him that she would, but that she only wanted to try on the weapons first, so she could see if the gear he had made was fit for Achilles. She was actually the same size as him.
Once Hephaistos agreed on this, Thetis armed herself and fled. Because he was incapable of grabbing her, he took a hammer and hit Thetis in the ankle. Injured in this way, she went to Thessaly and healed in the city that is called Thetideion after her.”
Φύλαρχός φησι Θέτιν πρὸς ῞Ηφαιστον ἐλθεῖν εἰς τὸν ῎Ολυμπον, ὅπως ᾽Αχιλλεῖ ὅπλα κατασκευάσηι, τὸν δὲ ποιῆσαι. ἐρωτικῶς δὲ ἔχοντα τὸν ῞Ηφαιστον τῆς Θέτιδος, οὐ φάναι ἂν δώσειν αὐτῆι, εἰ μὴ αὐτῶι προσομιλήσαι. τὴν δὲ αὐτῶι ὑποσχέσθαι, θέλειν μέντοι ὁπλίζεσθαι, ὅπως ἴδηι εἰ ἁρμόζει ἃ ἐπεποιήκει ὅπλα τῶι ᾽Αχιλλεῖ· ἴσην γὰρ αὐτὴν ἐκείνωι εἶναι. τοῦ δὲ παραχωρήσαντος ὁπλισαμένην τὴν Θέτιν φυγεῖν, τὸν δὲ οὐ δυνάμενον καταλαβεῖν σφύραν λαβεῖν καὶ πατάξαι εἰς τὸ σφυρὸν τὴν Θέτιν· τὴν δὲ κακῶς διατεθεῖσαν ἐλθεῖν εἰς Θετταλίαν καὶ ἰαθῆναι ἐν τῆι πόλει ταύτηι τῆι ἀπ᾽ αὐτῆς Θετιδείωι καλουμένηι.