diptych
noun[Gr., to fold.]
A public register of the names of consuls and other magistrates among pagans; and of bishops, martyrs and others, among Christians; so called because it sometimes two leaves folded, but is sometimes contained three or more leaves. The sacred diptych was a double catalogue, in one of which were registered the names of the living, and in the other the names of the dead, which were to be rehearsed during the office.