The Braahman, Aaranyak and Upanishad of the Rig Ved, Aitareya, is derived from Itara which means progressing from here (Ita means here) to the superior psychological planes (ra means movement).

Yaagyavalkya hails supreme among sages of sacred memory. As to his obtaining the Shukla Yajurveda Samhita from Bhagavan Surya, there is the following history.

Yaagyavalkya was the son of the sister of Vaishampaayan Jee, the Vedaacharya of the Taittireeya section of Yajur Ved. He was studying the Taittireeya Sanhitaa from Vaishampaayan Jee who was also his Guru. Vaishampaayan Jee had many other disciples too and they all were students of the Taittireeya Shaakhaa of Yajur Ved.

Once all the Rishi decided to form an association near the Meru mountain and made a rule that any Rishi who absented himself at the appointed hour should incur the sin of Brahm Hatyaa (the sin of killing a Braahman) for seven days. On that appointed day fell the Shraaddha ceremony of Vaishampaayan Jee's father. Vaishampaayan Jee thought, "Somehow I have to perform my father's ceremony. If the sin of Brahm Hatyaa comes to me, my disciples will observe the expiatory penance for me." So Vaishampaayan Jee did not attend the meeting of the Rishi. And accordingly he incurred the sin of Brahm Hatyaa.

Then Vaishampaayan Jee said to his disciples - "Now I have to expiate this great sin of Brahm Hatyaa. Therefore, you all will observe, for my sake, an expiatory penance for seven days."  Yaagyavalkya stood up at once and said - "O Guru, All these are poor-spirited young students. They will not be able to undergo such a hard penance. So, instead of all, I myself alone shall observe it in the manner in which nobody else can." Vaishampayana told Yaagyavalkya not to undertake it alone but Yaagyavalkya persisted. The preceptor was offended at this audacious attitude of the disciple and said - "O proud one, you are very conceited. You get away from me. Enough of you who is disposed to despise wise Braahman. Give back to me immediately whatever you have learnt from me."

Upon the order of the Guru, Yaagyavalkya, the son of Devaraat, vomited out the collection of the Yajus in the form of burning coals. The other disciples ate those burning coals taking the form of the Tittiree birds, because they were very eager to receive that knowledge. They then had the direct revelation of those Yajur Ved collections. As the Tittiree birds ate this Ved, it is thenceforth called the Taittireeya Yajur Ved. It is also known as Krishn (black) Yajur Ved on account of its being vomited substance.

After that Yaagyavalkya determined not to have any human Guru thereafter, so he began to propitiate the Sun-God, Soorya Dev. Yaagyavalkya worshipped and extolled the Sun, the master of the Ved, for the purpose of acquiring the fresh Vaidik portions not only known to his preceptor, Vaishampaayan, but to anyone in the world.

Yaagyavalkya said - "Prostration to the glorious Aaditya, who in the form of the Aatmaa, abides in all beings. I bow to Him who surrounds all like Aakaash, who is one and not separated or distanced by limiting conditions. O Great God, O Creator, I contemplate upon that glowing sphere which lights and warms the whole world. O God who burns all miseries wrought by unrighteous activities, who burns ignorance which is the seed of activity! O Lord, I worship Thy lotus-like feet praised and worshipped by the rulers of the three worlds. Give me those portions of the Ved which are not known to others."

The Sun-God, the glorious Lord Hari, pleased with Yaagyavalkya's penance, assumed the form of a horse and taught the sage such fresh portions of the Yajur Ved as were not known to any other. This portion of the Yajur Ved goes by the name of Shukla Yajur Ved. It is also known as Vaajsaneya Yajur Ved, because it was evolved in great rapidity by Soorya in the form of a horse through his manes. Yaagyavalkya divided this Vaajsaneya Yajurveda again into fifteen branches, each branch comprising hundreds of Yaju's Mantra. Maharshi Kanva, Madhyaandin and others learnt those branches.

In a sacrifice performed by King Janak, there was an exchange of words between Yaagyavalkya and Vaishampaayan Jee. But on hearing that Yaagyavalkya had obtained a fresh Ved from the Sun God, Vaishampaayan Jee was much pleased and he requested Yaagyavalkya to teach that Ved to his own disciples also. Yaagyavalkya consented and taught his Shukla Yajur Ved to the disciples of Vaishampaayan Jee.