Oh, I dunno, pfranz; a whole lot of air-force (and army) slang got into the language around the time of the "nd World War. "Prang", meaning crash, were used about motor accidents for years afterwards, so was "it's a bit if a bind", meaning that it was an onerous duty.
The popularity of airforce slang was probably enhanced by a radio comedy show called Much-Binding-in-the-Marsh starring Kenneth Horne and Richard Murdoch as Officer-in-Charge and subaltern on a mythical airfield, Much-Binding-in-the-Marsh, somewhere in southern England - the name itself is a skit on the type of village name common in those parts.
But the script was redolent with air force slang and some of it certainly became common usage. Having said that, i cannot recall that they ever used the expression, "pear-shaped."
However, there were other routes for slang to become common parlance.