According to the legend, there was a king of the yadava dynasty named "shurasena" who had a beautiful young daughter named Pritha (Kunti).
A rishi (Vedic scholar and seer) named durvasa visited the king for a lengthy stay and was housed as his palace guest.
Shurasena asked pritha to ensure that durvasa's stay was comfortable. On leaving, having been delighted with his stay and her diligent services, durvasa thanked her and gave her the siddha mantra (a type of chant), telling her that if she ever wants, she can invoke any deity to give her a child.