Because he was born on an island, he was called Dvaipayana. That learned (Dvaipayana), knowing that Dharma would become lame by one leg at each Yuga,
न्यस्तो द्वीपे स यद्वालस्तस्माद्वैपायनः स्मृतः। पादापसारिणं धर्मं स तु विद्वान्युगे युगे॥