According to one theory, the characters used for this term (which, although pronounced "yashi", is written "kagushi") developed from Kagutsuchi (Honokagutsuchi no kami), the god of fire who appears in the "Kojiki" (The Records of Ancient Matters), and who kills his mother, Izanami, by burning her vagina as he was being born before being chopped to pieces by his father, Izanagi, the many pieces turning into gods.
その語源は一説によると、『古事記』にも登場する火の神で、出雲国にて出産時に産道を焼いてイザナミを死に追いやりイザナギに切り刻まれて沢山の神に分裂したカグツチ（ほのかぐつちのかみ）の加具土が“加具士→加具師→香具師”と変化したもの。