“Soota said, ‘That Brahmana of rigid vows (Jaratkaaru) then wandered over the earth for a wife but he did not find a wife. One day he went into the forest, and recollecting the words of his ancestors, he thrice prayed in a faint voice for a bride (wife). Immediately, (the snake or Naagaa) Vaasuki rose and offered his sister for the Rishi’s (Jaratkaaru) acceptance. But the Brahmana (Jaratkaaru) hesitated to accept her, thinking her (Vaasuki’s sister) may not to be of the same name with himself. The high-souled Jaratkaaru thought within himself, ‘I will not accept for wife who does not have the same name as myself (i.e. I accept your sister only if her name is Jaratkaaru).’ Then that Rishi (Jaratkaaru) of great knowledge and strict Tapas asked him (Vaasuki), saying, ‘Tell me truly what is the name of this your sister, O Naagaa (Vaasuki).’
“Vaasuki replied, ‘O Jaratkaaru, this my younger sister is called Jaratkaaru. Given away by me, accept this slender-waisted lady for your wife. O best of Brahmanas (Jaratkaaru), for you I reserved her. Therefore, take her.’ Saying this, he (the snake Vaasuki) offered his beautiful sister to Jaratkaaru who then accepted her with ordered rites (as said in Shaastraas).’”
SRIMAD MAHABHARATA – AADI PARVA – AASTIKA (UPA) PARVA – PART 14 – JARATKAARU: VAASUKI’S SISTER