An expression that means powering through a situation, to push it to the limit, to the max, to go all out, or to give it all you’ve got. Some people say the origin has to do with steam engines during past centuries, but the phrase as used today has its origin in the Air Force where it was slang for what’s involved to achieve maximum G-Force given that the throttle controls often have ball-shaped nobs at the top. The expression has nothing to do with testicles.