In today's language the phrase "Balls to the wall" means to push the limit, to go full speed. Many believe the phase has a "dirty" connotation, but that is not the case. The phrase is actually a reference to the throttle on planes. When you wanted to accelerate, the throttle would be pushed toward the firewall. When you wanted to go as fast as possible you would push the throttle with it's ball all the way to the wall. Hence, the phrase balls to the wall was born. The first time it was used is believed to be during the Korean war, it is likely related to the phrase "balls-out" from WWII, which has the same meaning.

-Professor Walter