"Tome" comes ultimately from the Greek verb "temnein," which means "to cut." "Temnein" gave rise to a related Greek noun, "tomos," which means "scroll of papyrus." To make a scroll of papyrus, several papyrus reeds had to be cut down, cut open, scraped out with a knife, and then laid in layers to form the papyrus--you can see how a verb meaning "cut" would be involved in the creation of a word meaning "scroll of papyrus." Scrolls of papyri often contained sections of larger documents, and the Greek word "tomos" eventually came to mean "one volume of a larger work." The word moved through Latin to Middle French, and then to English as "tome."