Where does the term supercharged come from..........

Source - Wikipedia.org

A supercharger (also known as a blower) is an air compressor used to force more air (and hence more oxygen) into the combustion chamber(*) of an internal combustion engine than can be achieved with ambient conditions atmospheric pressure.

The additional mass of oxygen-containing air that is forced into the engine improves on its volumetric efficiency which allows it to burn more fuel in a given cycle - which in turn makes it produce more power. A supercharger can be powered mechanically by belt, gear, or chain-drive from the engine'* crankshaft. It can also be driven by a gas turbine powered by the exhaust gases from the engine. Turbine-driven superchargers are correctly referred to as turbo-superchargers - or more commonly as turbochargers.