Jahnu is an ancient sage in Hindu mythology connected with the story of Ganga. When the celestial Ganga flowed to earth from the heaven, the hermitages of Jahnu and other saints were flooded and washed away by the current of the river. Jahnu was so enraged that he drank the entire river water by using his Yogic power.
The gods and saints requested him to release Ganga so that she could proceed in her mission to release the souls of the ancestors of king Bhagiratha. Jahnu then released the river through his year and henceforth Ganga is known as `Jahnavi` or the daughter of Jahnu.
In another version of the story sage Jahnu was angered as while he was enchanting Gayatri, his `Acamana cup` fell into the ganga and swept away by the currents. In this story King Bhagiratha pacified sage Jahnu by his penance to release Ganga.
