Callisto

in classical mythology a nymph, mother of Arcas by Zeus, turned to a bear by Hera, from Greek kallistos, superlative of kalos "beautiful, beauteous, noble, good," and its derived noun kallos "beauty," from *kal-wo-, which is of uncertain origin, perhaps related to Sanskrit kalyana "beautiful." The usual combining form in Greek was kalli- "beautiful, fine, happy, favorable;" kalo- was a later, rarer alternative form. Also the name given 17c. to the fourth moon of Jupiter. Feminized as proper name Callista.