DIPTYCHA, in Antiquity, a public register, wherein were written the names of the consuls and other magistrates, among the heathens; and of bishops, and defunct as well as surviving brethren, among the Christians.
The word is formed from the Greek διπτυχον, or διπτυχα, and that from διπτυξ, a masculine noun derived from πτυξαι, I fold or plait. From its future πτυξω is formed πτυξ, a fold or plait, to which adding dis, twice, we have διπτυξ, in the genitive διπτυχον, whence comes the nominative neuter διπτυχον, a book folded in two leaves; though there were some in three, and others in four or five leaves. An ingenious author imagines this name to have been first given them in order to distinguish these leaves from the books which were rolled, and hence called volamina.
It is certain there were profane diptycha in the Greek empire, as well as sacred ones in the Greek church. The former were the matricula or registers, wherein the names of the magistrates were entered; in which sense diptycha is a term in the Greek chancery.