1911 Encyclopædia Britannica/Epinaos

EPINAOS (Gr. ἐπί, after, and ναός, a temple), in architecture, the open vestibule behind the nave. The term is not found in any classic author, but is a modern coinage, originating in Germany, to differentiate the feature from “opisthodomus,” which in the Parthenon was an enclosed chamber.