It is also called 'hondo' (main hall) since the principle image, the standing statue of Amida Nyorai (Amitabha Tathagata), is enshrined at the butsuma, but from bokusho (writing in India ink) and other articles found when repairing with dismantling, it is understood that it was called 'Oshoin' at the time of construction.
仏間に本尊阿弥陀如来立像を安置することから「本堂」とも呼ぶが、解体修理の際に発見された墨書等から、建設当時は「大書院」と称されたことがわかる。