Yes! I have a name for it!
I remembered to ask my brother about the insanely heavy-for-it’s-size object I’d dug out of the grass.
He called it a worm drive.
Inside are gears that convert the energy from high speed rotation into slow speed rotation with high power.
I did some searches and found it under terms like worm gear box, worm reduction drive, worm gear reducer, and so on. I even found some similar to ours, though none quite like it. It even looks like the Ohio brand is still around.
Another one of those “ah, one of those things I understood but didn’t know the name of.”
Definitely something we want to try and protect from further damage!