Volvelle

Part of speech: noun

Pronunciation: /ˈvɒlˌvɛl/

Definitions

1. A device with circular components that rotates to assist in calculations or visual representations in scientific contexts
2. An instrument employing rotating disks to facilitate data analysis or celestial predictions in various fields
3. An apparatus featuring interlocking circular sections that turns to aid in mathematical computations or graphical illustrations in scientific applications

Etymology: The volvelle is a paper or parchment instrument built from stacked rotating disks, and its name comes from the Latin verb "volvere," meaning "to turn" or "to roll." Medieval scholars used these devices to work out astronomical positions, calendar dates and calculations, turning the wheels to line up scales and read off results. The English word was borrowed through Middle English from Medieval Latin "volvellum" and "volvella," which were formed from "volvō," the Latin for "I turn," with the diminutive ending "-ellum," giving something like "little turning thing." The Latin form reflects the mechanism itself: the defining feature of the device is the movement of its discs, and the name describes that motion directly.