Persia is the old name for the country now called Iran. Reza Shah Pahlavi changed the name to Iran, the land of the Aryans, in 1935. The name Persia comes from the country's southern province, Fars, from where the Achaemenids came to establish the original Persian Empire of Cyrus the Great in 550 BCE. Persian (Farsi) is the national language of Iran, but many of its people speak variants of Turkish, Kurdish, and Arabic. Kurdish is related to Persian. Historically, Persia has been closely associated with the Kurds, who are ethnically related to the Persians but ethnically distinct from the Arabs and Turks.
In 1514, the Ottoman sultan Selim Yavuz (the Grim) defeated Shah Ismail of the Safavid Persians at the famous Battle of Chal-diran northeast of Lake Van in what is now eastern Turkey. In the succeeding centuries, Kurdistan became a frontier between the two empires and suffered accordingly. In addition, both empires deported entire Kurdish tribes. Their descendants still live today in areas south of Ankara, Turkey, and in the province of Khorasan, Iran, some 1,000 miles east of their original homeland and even farther east in Afghanistan's Hindu Kush Mountains. The Treaty of Zuhab in 1639 established the boundary that basically still exists today between Turkey and Iran.
Historical Dictionary of the Kurds. Michael M. Gunter.