However, it is believed that they were regarded as a synonym in the period of "the Kojiki (Records of Ancient Matters) and the Nihonshoki (Chronicles of Japan)," because they were both acts of removing sins and impurities which the Shintoism considered to be taboo for the purification of a pure mind and body.
しかし、ともに神道において禁忌とされている罪や穢を除去して心身を清める行為であることから、すでに記紀の段階において同一視されていたと考えられている。