Srimad Bhagavatam Canto 05, Chapter 07, Text 03

SB 5.7.3

ajanabham namaitad varsam bharatam iti yata arabhya vyapadisanti.
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Formerly this planet was known as Ajanabha-varsa, but since Maharaja Bharata’s reign it has become known as Bharata-varsa.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
This planet was formerly known as Ajanabha because of the reign of King Nabhi. After Bharata Maharaja ruled the planet, it became celebrated as Bharata-varsa.
Srimad Bhagavatam Canto 05, Chapter 07, Text 02
Srimad Bhagavatam Canto 05, Chapter 07, Text 04