Lewis & Short

1. caudex, ĭcis, m. (more recent orthography cōdex) [etym. dub.; cf. cauda].

  1. I. The trunk of a tree, the stock, stem (rare).
          1. (α) Caudex, Plin. 16, 30, 53, § 121; 12, 15, 34, § 67; Verg. G. 2, 30 et saep.
          2. (β) Codex, Ov. M. 12, 432; Col. 4, 8, 2; 5, 6, 21.
            Hence,
    1. B. The block of wood to which one was bound for punishment: codex, Plaut. Poen. 5, 3, 39; Prop. 4 (5), 7, 44; Juv. 2, 57.
    2. C. A term of reproach, block, dolt, blockhead: caudex, Ter. Heaut. 5, 1, 4; Petr. 74.
  2. II. Inpartic.
    1. A. A block of wood split or sawn into planks, leaves or tablets and fastened together: quia plurium tabularum contextus caudex apud antiquos vocatur, Sen. Brev. Vit. 13, 4: quod antiqui pluris tabulas conjunctas codices dicebant, Varr. ap. Non. p. 535, 20.
      Hence,
    2. B. (Since the ancients orig. wrote upon tablets of wood smeared with wax.) A book, a writing (its leaves were not, like the volumina, rolled within one another, but, like those of our books, lay over one another; cf. Dict. of Antiq.).
          1. (α) Caudex, Cato ap. Front. Ep. ad M. Ant. 1, 2.
          2. (β) Codex, Cic. Verr. 2, 1, 46, § 119; id. Clu. 33, 91; Quint. 10, 3, 28; Dig. 32, 1, 52 al.
    3. C. Esp. of an accountbook and particularly of a ledger (while adversaria signifies the waste-book; hence only the former was of any validity in law): non habere se hoc nomen (this item) in codice accepti et expensi relatum confitetur: sed in adversariis patere contendit, etc., Cic. Rosc. Com. 2, 5; v. the passage in connection; cf. id. ib. 3, 9: in codicis extremā cerā (i. e. upon the last tablet), id. Verr. 2, 1, 36. § 92: referre in codicem, id. Sull. 15, 44.
    4. D. A code of laws: Codex Theodosianus, Justinianus, etc.; cf. Dict. of Antiq. s. v.

cōdex, ĭcis, v. caudex.