In my story, my characters live in the wilderness, and they have no modern technology. They do see ruins from the past (from now) but other than that they have no idea how advanced other parts of the world might be, or of technology of the past. However, they often see the plane of a more advanced civilization (they are monitoring them to stop them from getting better technology) flying over them. It is thin and grey, very efficient but not too hard to see. I don't want these people, after seeing the plane for hundreds of years, to look up at it and go, 'it looked like a metal bird' because that seems so cliche. I want it to be clear that they have become so used to seeing it that it has been incorporated into their vocabulary. What word could I have them use for it instead? Honestly I would take anything that sounds like a real word and isn't super cheesy.
They're British, if that helps.