I learned in college what the term “balls out” really means. In the old days of steam engines, the speed was controlled by a govervnor that used centrifugal (or centripetal, if you prefer) force. The faster the engine went, the farther out the balls on the governor would swing, or fly. It was referred to as a “fly ball governor” since the balls fly out at high speed. Thus, when the engine is going fast, the engine is going “balls out.” The term “balls to the wall” is a variation of the same thing.