Passage 3.19.8
Θηρίταν δὲ ἐπονομάζουσιν ἀπὸ Θηροῦς, ταύτην γὰρ τροφὸν εἶναι τοῦ Ἄρεως λέγουσι. τάχα δʼ ἂν ἀκηκοότες παρὰ Κόλχων Θηρίταν λέγοιεν, ἐπεὶ Ἔλληνές γε οὐκ ἴσασιν Ἄρεως τροφὸν Θηρώ· δοκεῖν δέ μοι Θηρίτας οὐ διὰ τὴν τροφὸν ἡ ἐπωνυμία τῷ Ἄρει γέγονεν, ὅτι δὲ ἀνδρὶ χρὴ πολεμίῳ καταστάντα ἐς μάχην οὐδὲν ἔτι ἔχειν ἤπιον, καθὰ δὴ καὶ Ὁμήρῳ περὶ Ἀχιλλέως πεποίηται λέων δʼ ὣς ἄγρια οἶδεν. Hom. Il. 24.41
They call him Theritas after Thero, whom they say was Ares' nurse. Possibly they have heard this name Theritas from the Colchians; at least the Greeks know no nurse of Ares named Thero. But in my opinion, the epithet Theritas was not given to Ares on account of any nurse, but because a warrior, when entering into battle with an enemy, must put aside every gentleness—a point similarly expressed by Homer regarding Achilles: "Like a lion, he knows savage ways."