A river. According to the Bakabrahma Jātaka, one of Baka's good deeds which brought him rebirth in the Brahma-world was that of having set free the inhabitants of a village on the banks of the Enī (Enikūle), when the village was raided.
Baka was then an ascetic named Kesava and the Bodhisatta was his disciple Kappa. S.i.143; J.iii.361; SA.i.163.