Diptycha

Lat. [Gr. diptycha, two leaved.] Diptychs; tablets of wood, metal or other substance, used among the Romans for the purpose of writing, and folded like a book of two leaves. The diptychs of antiquity were especially employed for public registers. They were used in the Greek, and afterwards in the Roman church, as registers of the names of those for whom supplication was to be made, and are ranked among the earliest monastic records.

Hubback's Evid. of Succession, 567. Encyclop. Amer.