The term has been common here in Canada going back into the 1970's. I'm not sure where the Aussie reference originally came in, but the two eggs comment early on in the thread was what I heard in the late 1980's up here. I believe there are references to "breakfast" in both the OVLR and Association of Land Rover Owners of Canada newsletters going back more than twenty five years.
Cooking on it? There were a couple of grilles made that doubled as BBQ grilles, the last I saw Jeff Meyer had. In the shape of a Series III grille, complete with fold out legs to use as a BBQ grille. But nobody ever thought to use a real one over a fire to cook with, despite being fairly common items.
Despite the mystic, it is a great term, and considering how it spread rapidly, despite unknown origins, from Canada at least, shows how accurate and applicable the term really is. I would not say that there is a small group of Canadians laughing every time they see it used. It is not a joke and Terriann is disparaging Canadians for suggesting that this was maliciously done as some sort of joke. If true, why would we use the term commonly here to describe this part of a Land Rover?