Idiom Du Jour

At the behest of my family, I've decided to start a periodic type of entry in which I define and investigate the roots of some interesting idiomatic expressions.

...And although the title of this installation is in French, I will in fact be defining (and perhaps debunking) English phrases exclusively.

First off, this gem: balls to the wall.

Definition: to go all out, to push the limits.

Origins: (Firstly, let me just note that I am in no way a proper professional etymological investigator...all I've got is the internet at my fingertips...a small selection of wordy-type books...and a limited amount of patience and interest.  Although...) however raunchy this one may appear, it turns out that everyone on the world wide web is assuring me it started out quite innocent and doesn't refer to male anatomy in any way.  From there, I have two or three possible explanations.  Firstly, the expression is said to originate in the particular speech used by pilots during World War Two.  According to this, the throttle and fuel controls are topped with joystick-esque ball grips, and so to go ahead at top speed, 'full throttle' (as it were), one pushes the aforementioned balls towards the front wall of the cockpit.  Makes sense.

Before I conclude this episode, however, I ought to mention a possible usage of this idiom that would pre-date the aeronautical one mentioned above.  In this instance, we aren't so much concerned with planes, but trains...or possibly submarines (sorry, no automobiles).  Have I mentioned I'm no engineer?  Well anyway, as near as I can make out, these types of machines have generators, or drive-shafts, or counterweights, or something equipped with metal balls which get slung about.  There's probably a wall involved as well; regardless (yes...can you tell my interest is waning?) the end result is roughly the same: balls to the wall means full speed ahead.