A certain goddess, having been impregnated by Zeus, was driven from her home by the ever-angry Hera, and forced to flee, with her children or child, unsure. Everywhere she went she was rejected in fear of Hera's wrath. At one notable place she stopped to rest and some rude men drove her away. A god or goddess saw this and changed them into frogs.
According to this story:
The goddess approached, and kneeling on the bank would have slaked her thirst in the cool stream, but the rustics forbade her.
When the people reject her, Latona turns them into frogs:
Latona was so angry that she ceased to mind her thirst. She no longer supplicated the clowns, but lifting her hands to heaven exclaimed, “May they never quit that pool, but pass their lives there!” And it came to pass accordingly. They now live in the water, sometimes totally submerged, then raising their heads above the surface or swimming upon it. Sometimes they come out upon the bank, but soon leap back again into the water. They still use their base voices in railing, and though they have the water all to themselves, are not ashamed to croak in the midst of it. Their voices are harsh, their throats bloated, their mouths have become stretched by constant railing, their necks have shrunk up and disappeared, and their heads are joined to their bodies. Their backs are green, their disproportioned bellies white, and in short they are now frogs, and dwell in the slimy pool.”’
Latona is the Latin version of the goddess Leto, famous as the mother of Artemis and Apollo.
As Wikipedia says:
In Roman mythology, Leto's equivalent is Latona, a Latinization of her name, influenced by Etruscan Letun.