From kephale; properly, a knob, i.e. (by implication) a roll (by extension from the end of a stick on which the manuscript was rolled) -- volume.
see GREEK kephale
1. a little head (Latincapitellum, capitulum).
2. the highest part, extremity or end of anything; as the capital of a column, 1 Kings 7:9, 31 etc.; Geoponica 14, 6, 6; hence, the tips or knobs (theumbilici of the Romans (or rather the cornua; see Gardthausen, Griech. Palaeogr., p. 52f; Rich, Dictionary, under the word umbilicus)) of the wooden rod around which parchments were rolled seem to have been called κεφαλίδες, because they resembled little heads; so that
3. the Alexandrian writers transferred the name κεφαλίς to the roll or volume itself: ἐν κεφαλίδι βίβλου, Hebrews 10:7 (from the Sept. of Psalm 39:8 STRONGS NT 2777b: κημόωκημόω, κημῷ: future κημώσω; (κημός a muzzle); to stop the mouth by a muzzle, to muzzle: βοῦν, 1 Corinthians 9:9 T Tr WH marginal reading (Xenophon, r. eq. 5, 3); see φιμόω.