In the year 899 when Retired Emperor Uda entered the Buddhist priesthood, the term referred to a member of the aristocracy or the Imperial Family who entered the Buddhist priesthood and joined the Retired Emperor at Ninna-ji Temple inge named 'Omuro.'
元は昌泰2年（899年）の宇多上皇出家の際に、上皇とともに仁和寺の院家の1つであった「御室」に付き従って出家した皇族・貴族達を指した。