According to chronicles, prince Giri-aba and princess Somawathi (sister of King Kavanthissa) lived on a small community called "Somapura" on the beds of Mahaveli River. Price Giriaba constructed Somawathi Chethiya on the request of his wife who wanted to engage in religious activities. Upon completion of the Stupa, the prince requested a monk named Mahinda for some "dathu" to be kept in the relic chamber of the stupa. Maha Thera
Mahinda gave him the right tooth relic of Lord Buddha. According to history this tooth relic was received by a "Na" (serpent) king Jayasena when the remaining relics from the Buddha"s cremation site were distributed. He took this to the "Naga Lokaya" (the kingdom of serpents) and deposited it in a stupa made out of gold for worship. When the prince Giriaba"s request was made, the maha thero Mahinda visited the "Naga" Kingdom and brought this tooth relic to be deposited in the stupa built by the prince.