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When did Isfahan become known by its regional name?

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Isfahan, Iran: Masjed-e Emām (“Imam Mosque”) — Isfahan Masjed-e Emām (“Imam Mosque”), Isfahan, Iran.

Following the Arab conquest in 642 CE, the city came to be known by the regional name Isfahan. Prior to this, the site was known by names such as Gabae, Gay, and Jayy.1