A name of Vishnu as ‚The friend/helper of Indra‚. Indra is also called Mahendra, Maha Indra, the great Indra.
Indra and Vishnu are Mahendra and Upendra.
In myths, the Gods usually go to Brahma when they have difficulties. He goes to Indra with them and if he cannot help, Vishnu is visited. He always has the solution.