Finding Bob B's aside on Celtics a little hard to take, being a bit Celtic as well as everything else, I assert that nobody knows NOR could know where the tune came from, who wrote and when SINCE it is a very simple melody and there are Libraries of Books of Music containing the theme, all predating not just AG but the Colonies as well.


So without too much effort I can think of a bunch of popular ancient folk tunes that express the AG theme without looking into Classical lore.

In fact the American, and lately I notice the Australian, way is to hash up some already established folk tradition and call that it's own.