'Mountain-king'. It refers to sanno gongen the pre-Meiji name of the guardian deity of Mt. Hiei north-east of Kyoto, site of the great temple-shrine complex formed around the Tendai Buddhist Enryaku-ji originally founded by Saicho (Dengyo Daishi). The mountain deity is Onamuchi (another name for Okuni-nushi) of the Eastern shrine or Oyamakui or Yama-sue-no-o-nushi of the Western shrine of the Hiyoshi or Hie taisha on Mt. Hiei, and is also identified with Amaterasu. Hie taisha is the head shrine of nearly forty thousand Hie branch shrines throughout Japan.
A Popular Dictionary of Shinto. Brian Bocking.