noun
also vol·vell ˈvälˌvel
( -s )
Etymology: Middle English volvelle, probably from Medieval Latin volvella, from Latin volvere to roll, turn + -ella
: an old contrivance for ascertaining the time of the rising and setting of the moon and sun and the time of high and low tide consisting of one or more movable circles with pointers and figures of the moon and sun which are placed upon several graduated and figured circles drawn on the leaf of a book