Yaagyavalkya Rishi was a great Rishi. He was the disciple of Vaishampaayan Jee (and Vaishampaayan Jee was the disciple of Ved Vyaas Jee). When the great sage Ved Vyaas Jee divided Ved in four parts and taught them to his various disciples, he taught Yajur Ved to Rishi Vaishampaayan Jee. Rishi Vaishampaayan Jee, in turn, taught that Ved to his disciple Yaagyavalkya Jee.

On one occasion Vaishampaayan Jee got angry with Yaagyavalkya Jee, so he asked him to leave everything whatever he learnt from him. Yaagyavalkya immediately vomited all the Yajur Ved's Mantras and departed. Seeing the Ved Mantra lying on the ground, many other Rishi assumed the form of partridges (Teetar) and ate them up. When they taught these Ved Mantras to their disciples, this branch was called Taittireeya (descended from partridges) branch of Yajur Ved.

Yaagyavalkya was now in search of better knowledge, so he did Tap for Soorya Dev and Soorya Dev pleased from his Tap appeared before him in the form of a horse (Vaaji) and imparted him Yajur Ved Mantras which were unknown to anyone else, even to his Guru Vaishampaayan Jee. He then divided those hymns into 15 rescensions, known as Vaajsaneya (descended from a horse's mane) branch of the Yajur Ved.