Of Ṛṣabhadeva’s one hundred sons, the eldest, named Bharata, was a great, exalted devotee qualified with the best attributes. In his honor, this planet has become known as Bhārata-varṣa.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
येषां खलु महायोगी भरतो ज्येष्ठः श्रेष्ठगुण आसीद्येनेदं वर्षं भारतमिति व्यपदिशन्ति
yeṣāṃ khalu mahāyogī bharato jyeṣṭhaḥ śreṣṭhaguṇa āsīdyenedaṃ varṣaṃ bhāratamiti vyapadiśanti
SB 5.4.9