This one is based on a story told by the Adi Minyong tribe of Arunachal Pradesh.
The Story-
These days there is only a plant called kojam koja, but once it was the name of a flourishing village. In Kojam Koja there lived a Boy, Kosam Luntong, and one day he proposed that the village should hold a festival to the spirits. So the people of the village went out fishing and they saw a huge fish-like creature caught in one of the nets. The fish, was the son of Biri Borte, the strong king of the water kingdom. This big fish was taken back to the village and eaten at the feast. A bat carried the news of this to Nippong, queen of the water kingdom, who called on all the powers of water to rise and destroy Kojam Koja. All the people that were in it were buried in its ruins. But the heads of the people have sprung up as the chestnut tree and their other members have sprung up as the different kinds of bamboo, and the plants known as kojam koja.