According to the mythical account of the Kojiki, Onogoro Island was created when the divine couple Izanagi and Izanami churned the sea with a jewelled spear from their vantage point on the floating bridge of heaven. When they raised the spear from the ocean, drops fell from the spear, forming the island. They built a palace on top with a great column in the middle. The couple walked around this pillar in opposite directions, and when they encountered each other, they were wed. This island is where Hiruko was conceived.
The name probably signified "self-curdling island".
In his Kojiki-den, a ground-breaking commentary on the Kojiki, the great Kokugaku scholar Motoori Norinaga asserted that it referred to one of the small islands northwest or southwest of Awajishima. However, attempts to identify places in mythical cosmology with known sites in a real country's topography remain unconvincing.
- Kurano, Kojiki, page 53
- Philippi's translation, p. 49, p. 57, and p. 306.