Research of the historical literature revealed that the practice of re-stringing standard violins with large diameter strings in order to play an octave lower has been around for quite some time, possibly hundreds of years. There is anecdotal evidence that more than a few early 20th Century jazz violinists/fiddlers made their own octave fiddles in such a manner. We would love to learn more about use of octave violins by early jazz musicians...use the FEEDBACK feature on the navigation bar at the top of the screen.
This practice was brought out of obscurity arguably most effectively by a 1992 article in Strings Magazine by the famous Violist/Fiddler, Darol Anger.
Except in the case of electric instruments, such as one used by Jean Luc Ponty on a 1975 recording, octave violins/fiddles in their acoustic form have been thought to be, of necessity due to their small size, quiet instruments requiring amplification when played in an ensemble of instruments. For many designers of innovative musical instruments, coming up with an acoustic baritone violin with good projection and deep timbre can seem like overcoming the known laws of physics.