This sinister Ford Galaxie is not a metaphorical rocket, as in "fast as a rocket!" It is not a marketing trademark like Oldsmobile's Rocket 88. This car actually is rocket-powered. In addition to the prodigious amount of power created by the supercharged 427 engine topped with four side draft carburetors, there is a genuine rocket engine affixed to the differential that generates an extra 1000 horsepower.
Here's another interesting excerpt regarding the rocket axle:
The infamous Black Widow Volkswagen Beetle, a basically stock Bug fitted with a Turbonique Rocket Drag Axle, instantly became a drag racing legend by leaving Tommy Ivo’s four-engine Showboat dragster in its dust with a 9.36 elapsed time at 168 mph on Sept.19, 1966, at Tampa Dragway.