PURPORT

Gargamuni did disclose to Nanda Maharaja that Balarama would be known as Saṅkarsana because of uniting two families-the yadu-vamsa and the vamsa of Nanda Maharaja-one of which was known as ksatriya and the other as vaisya. Both families had the same original forefather, the only difference being that Nanda Maharaja was born of a vaisya wife whereas Vasudeva was born of a ksatriya wife. Later, Nanda Maharaja married a vaisya wife, and Vasudeva married a ksatriya wife. So although the families of Nanda Maharaja and Vasudeva both came from the same father, they were divided as ksatriya and vaisya. Now Baladeva united them, and therefore He was known as Saṅkarsana.