Didascalicon, Book IV: the order and number of the divine books
Chapter IV. On the library
Bibliotheca took its name from the Greek, because books are stored there. For biblion is of books, theke is interpreted repository. The library of the Old Testament Esdras the scribe restored, moved by the divine Spirit, after the Law was burned by the Chaldeans, when the Jews returned to Jerusalem; and he corrected all the volumes of the Law and the Prophets which had been corrupted by the Gentiles, and made the whole Old Testament twenty-two books, that there might be as many books in the Law as there are letters. Moreover, five letters are double among the Hebrews, caph, mem, nun, phe, sade; for they write differently through these the beginnings and middles of words, differently the ends. Hence also five books are thought by most to be double: Samuel, Malachim, Dabre iamin, Esdras, Jeremias with his Kinoth, that is, his Lamentations.