Opinions divide concerning its origin: some insist Ushioni was sanctified as mentioned above; a folktale says two men in Iyo Province named Zusho TONAI and Heinojo KURAKI did away with Ushioni; another folktale says a man from Iyo did away with Ushioni living in Kaifu County (of Tokushima Prefecture), Tokushima Prefecture; and another folktale says Kiyomasa KATO produced tortoise wagons to frighten tigers in Korea before Japan's invasion of Korea by Hideyoshi TOYOTOMI.
由来は前述のように牛鬼を神聖視する説のほか、伊予国の藤内図書と蔵喜兵ノ尉という人物が牛鬼を退治したという話、徳島県海部郡(徳島県)の牛鬼を伊予の人物が退治したという話、豊臣秀吉の朝鮮出兵の際に加藤清正が朝鮮の虎を脅すために亀甲車を作った話など、諸説ある。