It is said that the boat-shape originated from a fable in which, in 847, when the founder of Saiho-ji Temple Jikaku Daishi Ennin was caught in a rainstorm on his way home from Tang he chanted Myogo (the name of Buddha) saying, 'Namu Amida Budda' and was able to return to Japan safely.
船の形は、承和(日本)14年（847年）、唐からの帰路に暴風雨にあった、西方寺の開祖・慈覚大師円仁が「南無阿弥陀仏」と名号を唱えたところ無事到着できたという故事にちなむという。