sa vai sapta sama garbham
abibhran na vyajayata
jaghne ’smanodaram tasyah
so ’smakas tena kathyate
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Madayanti bore the child within the womb for seven years and did not give birth. Therefore Vasistha struck her abdomen with a stone, and then the child was born. Consequently, the child was known as Asmaka [“the child born of a stone”].