Souped-up

This expression is most commonly associated with motorcars that have had their performance enhanced, usually by increasing the power output of the engine. Its origin is American and is most likely associated with the supercharger device, which increases the pressure of the fuel/air mixture of a petrol engine. The first supercharger made its appearance around 1918. A supercharged engine soon became one that was souped up by the 1920s. Quite why the spelling should become souped as opposed to suped is not clear. It might have occurred through confusion with an American horseracing term, ‘soup’, which, according to Webster’s Dictionary in 1911, was any material injected into a horse with a view to changing its speed or temperament. One assumes Webster meant improving the horse’s speed or temperament rather than the opposite. Thus, in America, one could ‘supe’ up an engine or ‘soup’ up a racehorse. Either way the spelling has become entrenched on both sides of the Atlantic as souped up - an improbable win for the horse over the motorcar.