roots blower — The Roots type supercharger or Roots blower is a positive displacement type device which operates by pulling air through a pair of meshing lobes not unlike a set of stretched gears. Air is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust. The supercharger is driven directly from the engine's crankshaft via a belt or, in a two-stroke diesel engine, by spur gears.

It is named for the brothers Philander Higley and Francis Marion Roots, who first patented the basic design in 1860 as an air pump for use in blast furnaces and other industrial applications.

References: Wikipedia, the free encyclopedia – http://en.wikipedia.org/wiki/Roots_blower