Shellac and carnauba wax are both totally natural products. Shellac comes from Asia, mainly from India. It’s the resinous secretion of a small bug, and it has been used by humankind for millenniums. Shellac was one of the most dominant wood finishes until 1930’s. Nowadays it is still the most valued varnishing of wooden string-instruments.
About shellac you may read an interesting article from Wikipedia.