The members of the modern violin family are the violin, viola, cello, and double bass. These instruments are descendants of various kinds of medieval fiddles—fiddle, by the way, being an older word than violin—and the medieval fiddles themselves were bowed stringed instruments that were originally imported to Europe from the Middle East.
Up until the early 1500's the instruments of the modern violin family were still evolving, but by the mid-1500's, Italian craftsmen had created the models that, with minor modifications, have remained standard ever since. Quite a few four-hundred-year-old Italian instruments are still in use, in fact. If the instruments themselves were standardized early on, though, their names weren’t. For several centuries, the word viola, in Italian, was the generic term for any stringed instrument played with a bow, and it wasn’t until the 1700's that the term came to refer specifically to the instrument we now call the viola.