The origin of chimaki is believed to have been a thatch ring, which was carried on the waist by descendants of Somin Shorai, a poor man who warmly entertained Susano-o no Mikoto, one of Japan's primary gods, during his journey. The god promised the poor man that he and his descendants would be safe from pests forever, in requital for his generous act.

(From incomplete topographic records of ancient Hiroshima) Once upon a time, a northern god traveled to the south, and the sun set. At the place, there were two brothers named Somin Shorai and Kotan Shorai. Somin, the elder brother, was a poor man, while his younger sibling was rich and prosperous. When the god asked for a stay overnight, the richer gave a flat refusal. Somin, on the other hand, pleasantly ushered the traveler in, and entertained him with millet rice and millet-shell cushion. Years later, the god revisited Somin with his eight princes, and offered thatch rings designed to protect Somin and his family from pests, in requital for the night's accommodation. The god thus revealed his identity to Somin, saying, "I am the god of Susano-o. Whenever pests or plague prevail in the future, the rings would keep thee and thy children safe." The family survived even when all other villagers died from the plague, due to the protection of divine ring.