Didascalicon, Book IV: the order and number of the divine books
Chapter XVI. Certain etymologies of words pertaining to reading
A codex is of many books; a book is of one volume; and it is called codex by transference from the trunks of trees or of vines, as it were caudex, because it contains in itself a multitude of books like branches. Volume is so called from rolling. Liber is the inner bark of a tree, on which the ancients, before the use of paper or parchment, were wont to write. Hence they also called scribes librarii, whence the book is called a volume. Scheda, of which the diminutive is schedula, is a Greek name. A scheda is properly what is still being corrected and has not yet been reduced into books. The use of paper was first found at Memphis, a city of Egypt. It is called charta because the covering of the papyrus, plucked off piecemeal, is glued together, and so paper is made, of which there are several kinds. Parchment is named from Pergamum, where it was invented. They are also called membranes because they are drawn from the members of animals. Membranes were at first made of a yellow color; afterwards at Rome white membranes were discovered. A homily is called as it were a popular discourse, as where the word is made to the people. A tract is a manifold exposition of one matter. A dialogue is a conference of two or more; the Latins call it sermo. Sermo is so called because it is sown between both. Commentaries are so called as it were cum mente, with mind, or from comminiscor. For they are interpretations or commentaries of law or of the Gospel. Some say that commentaries should be the name for books of the Gentiles, but expositions for the divine. Glossa is Greek, and is interpreted tongue, because in a way it speaks the signification of the word beneath it. The philosophers call this adverbium, because it designates that word about which inquiry is made by one single word; for example, to be silent is to keep quiet.