Jahnavi – Name of river Ganga
Jahnavi means a female born from Jahnu
जाह्नवी – जह्नोः अपत्यं स्त्री
Since Rishi Jahnu released Ganga from his ear, therefore Ganga is considered as his daughter.
Story of Rishi Jahnu and Ganga
When Lord Shiva released Ganga from his hairs to place called Bindusara, from there the Ganga got divided into seven different streams.
Three streams Hladini ((ह्लादिनी), Pavani (पावनी) and Nalini (नलिनी) flowed eastwards and Suchakshu (सुचक्षु), Sita (सीता) and Sindhu (सिन्धु) three stream westwards.
The seventh stream called as Bhagirathi (भगीरथी) followed the chariot of King Bhagirath (भगीरथ)
In the path of the river Ganga, Rishi Jahnu (जह्नु) was performing a religious sacrifice and flow of ganga destroyed the place (यज्ञ-मंडप) .
Seeing the destruction rishi Jahnu got angry and drank the whole stream of river Ganga. When devatas, gandharvas prayed to the rishi to release the river, rishi Jahnu released the Ganga from his ear.
गङ्गां चापि नयन्ति स्म दुहितृत्वे महात्मन:।
ततस्तुष्टो महातेजाश्श्रोत्राभ्यामसृजत् प्रभु: !
तस्माज्जह्नुसुता गङ्गा प्रोच्यते जाह्नवीति च। – Ramayana, Balakanda, chapter 43 verse 37-38
They made Ganga daughter of Rishi Jahnu, and thereafter rishi Jahnu released Ganga from his ear. That is why Ganga is called as Jahnavi (जाह्नवी)
