I came across the tool pictured in my collection and cannot imagine its purpose. It's a long metal pick, with sharp studs running down it in a spiral. It ends in a tip that seems to be meant to make holes. It's very sturdy.
I would say that it's an older style drywall saw specifically for cutting curves.
You push the tip through the drywall (hammering the blue handle with your hand or other striking tool, if necessary) to make the hole, then run the tool in and out cutting with the saw teeth on the push stroke.
Since it's round, it will easily move in any direction, so when you reach a corner, you simply apply pressure to a different side of the handle and it'll cut in a different direction.
It's probably difficult to get a really straight line, but makes it very easy to cut holes for round boxes.
Now that I know these exist, I might just have to get one!
I've used one to clear the hole left in a car tyre, when the offending screw/bolt/sliver of metal has been removed. It reams out the existing hole so a mushroom plug can be put in, which then seals the hole. Not sure whether that practice is still legal all over the world, but it was a couple of decades ago in U.K.
Available in different diameters, and called a tyre reamer.