McG -

balls to the wall

The derivation I've always heard is that in most aircraft you push the "balls" - the knobs on the throttle, mixture, and prop pitch control levers, to the "wall" - the control panel, in order to "proceed at maximum speed."

A corollary implication not particularly well known is that most aircraft are/were designed to be capable of "emergency power" that will destroy the engines if sustained more than briefly, so that the meaning for those who know is:

At maximum speed and at risk.

"Modern" pilots refer to it as "full military power," or just "full-military," and most turbine engines are installed so that they can be operated at 105% or 110%, occasionally more, of "maximum sustained thrust" for brief periods in an "emergency."

No documentation at hand for this etiology though.

John