The Metamorphoses of Ovid, Books I-VII

The only probable solution of this story seems to have been the fact that there was in Caria, near the town of Halicarnassus, as we read in Vitruvius, a fountain which was instrumental in civilizing certain barbarians who had been driven from that neighborhood by the Argive colony established there. These men being obliged to repair to the fountain for water, and meeting the Greek colonists there, their intercourse not only polished them, but in course of time corrupted them, by the introduction of the luxurious manners of Greece. Hence the fountain had the reputation of changing men into women.

Possibly the water of that fountain, by some peculiar chemical quality, made those who drank of it become soft and effeminate, as waters are to be occasionally found with extraordinary qualities. Lylius Gyraldus suggests, that several disgraceful adventures happened near this fountain (which was enclosed by walls), which in time gave it a bad name.