Passage 9.32.3
τὸ δὲ πεδίον τὸ μεταξὺ τῶν ὀρῶν ἐκώλυεν οὐδὲν ἂν λίμνην ὑπὸ πλήθους εἶναι τοῦ ὕδατος, εἰ μὴ διὰ μέσου χῶμά σφισιν ἐπεποίητο ἰσχυρόν· καὶ οὕτω παρὰ ἔτος ἐς μὲν τὰ ἐπέκεινα τοῦ χώματος ἐκτρέπουσι τὸ ὕδωρ, τὸ δὲ ἐπὶ τὰ ἕτερα αὐτοῦ γεωργοῦσι. Θίσβην δὲ λέγουσιν ἐπιχώριον εἶναι νύμφην, ἀφʼ ἧς ἡ πόλις τὸ ὄνομα ἔσχηκεν.
The plain lying between the mountains would undoubtedly become a lake due to the abundance of water, were it not that a strong embankment has been built through its midst. Thus, each year, they divert the water beyond the embankment to one side, while they cultivate the land on the other side. They say that Thisbe was a local nymph, from whom the city took its name.