Early ancestors include the Arabic rebab and the medieval European Vielle, but later, more direct possible ancestors include the Venetian viole and the 15th- and 16th-century Spanishvihuela, a 6-course plucked instrument tuned like a lute (and also like a present-day viol)[4][5] that looked like but was quite distinct from the (at that time) 4-course guitar (an earlier chordophone).
Although bass viols superficially resemble cellos, viols are different in numerous respects from instruments of the violin family: the viol family has flat rather than curved backs, sloped rather than squarely rounded shoulders, c holes rather than f holes, and five to seven rather than four strings; some of the many additional differences are tuning strategy (in fourths with a third in the middle—exactly like a lute—rather than in fifths), the presence offrets, and underhand rather than overhand bow grip.
All members of the viol family are played upright between the legs like a modern cello, hence the Italian name viola da gamba (it. "viol for the leg"). This distinguishes the viol from the modern violin family, the viola da braccio (it. "viol for the arm"). A player of the viol is commonly known as a gambist.