Engu oshinke is written in Chinese characters as "院宮王臣家" and the character "院" refers to the Daijo Tenno (retired Emperor), the character "宮" refers to the Sangu (Empress, Empress Dowager and Great Empress Dowager) and the Togu (Crown Prince).
「院宮王臣家」の「院」とは太上天皇、「宮」とは三宮(皇后・皇太后・太皇太后)・東宮(皇太子)を指す。