It is based on enlightenment of Shinran, who is considered to be the founder of Jodoshin sect, in the position of hiso hizoku (non-priesthood, non-laity) by introducing himself to be 'Gutoku shaku Shinran' after being deprived of his priesthood due to banishment.
浄土真宗の開祖とされる親鸞が、流罪により僧籍を剥奪された後に、自らを「愚禿釋親鸞」と名告り非僧非俗の立場で教化された事に基づく。