Formerly this planet was known as Ajanābha-varṣa, but since Mahārāja Bharata’s reign it has become known as Bhārata-varṣa.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
अजनाभं नामैतद्वर्षं भारतमिति यत आरभ्य व्यपदिशन्ति
ajanābhaṃ nāmaitadvarṣaṃ bhāratamiti yata ārabhya vyapadiśanti
SB 5.7.3