Tūrān ("land of the Tūrya" like Ērān, Īrān = "land of the Ārya")I never realized the etymology of the name of Iran before.
Incidentaly, the A-to-E vowel change also gives us the name of England out of Angla-lond, as well as word pairs like man-men, Denmark-Dane, and even ultimately star-steer. In Old English this is called I-mutation, since you mutated the sound of the first vowel by anticipating the sound of the I in the following syllable. This mutation remained even after the syllable with the I, often a inflectional (grammatical) ending, had been dropped. There are other examples in Old English that don't look like they apply in Modern English because lots of Old English a's have become modern O's.* But if you allow for this, you can see the effect of I-mutation in pairs like whole/hale and heal (OE hal/hæl, halian), strong and strength (OE strang, strengþu), long and length (OE lang, lengþu), old and elder (OE ald, ieldra), know and knew (OE cnawan, cneow).
*This is where we get off having the O-sound represented by "oa" as in boat, throat, coat, etc. The A in Old English bat was pronounced close enough to an O that people noted it by writing an O next to the A. I assume the same origin for the Scandinavian letter Å, except scribes there wrote the O on top instead of to the side.