Thanks sidevalve. I've always thought it was probably an American expression, and your version is certainly better. I really only remember the reference to owl, excrement and slippery, and since I only flew with the chap once, in November 1957, have a bit of an excuse for not quite getting it right!
I would imagine there would be more occasion to use it at Keflavik, and now and again at Little Rissington, than in this neck of the woods just now!