1911 Encyclopædia Britannica/Coenaculum
COENACULUM, the term applied to the eating-room of a Roman house in which the supper (coena) or latest meal was taken. It was sometimes placed in an upper storey and reached by an external staircase. The Last Supper in the New Testament was taken in the Coenaculum, the “large upper room” cited in St Mark (xiv. 15) and St Luke (xxii. 12).