According to Wikipedia, viola da gamba is the Italian name for the viol, and means "viol of the leg," which also helped differentiate it from the visually similar but only distantly related early violin family which the Italians called viola da braccio (lit. "viol of the arm").
This particular viola da gamba has seven strings, for some fantastic bass, and is owned and played by Ronnee Fullerton of the Baroque Trio.
