I'msurprised that the origins of the term seem to have been lost have been lost. I'm sure I have known it most of my life, perhaps even before I first met my future brother in law before he married my sister in 1953. I know I started reading bits and pieces in the SMH before I started primary school in 1946, and there would have been a lot of discussion about this sort of thing as veterans returned to civilian life in the late forties. Particularly as my father was working in aircraft manufacture at the time, and would have talked about the use of aircraft.