Most of the written literature of ancient times was on continuous sheets of parchment or papyrus.
For convenience these sheets were wound into fairly tight rolls about sticks, one stick at either end of the roll.
In reading, the scroll was thus unwound from one stick and, as the reading proceeded, wound upon the other. The Latin term for the rolling of the scroll was volvo, to roll.
For that reason the thing which was rolled was anciently known as volumen, a derivative of volvo. When books were no longer rolled into scrolls, volume continued to be used, especially for a book of considerable size.
Further, from this notion of a book of considerable size, volume then acquired a second meaning, “any large quantity, any considerable amount.”
