This temple is named after King Boko (The legendary king in Loro Jonggrang Folklore) Ratu Boko means "Stork king".
However, the function of this place is more than just a place to pray, unlike the usual temples, Candi Ratu Boko is used to serve multiple functions, that are as a fortress, to serve the guests, a place of worship and as a caves. Ratu Boko itself is mix of Hindu and Buddhist culture.