origin: of the term "cube steak"?!
I can't find anywhere "why" it is called a cube steak.
Because tough meat is pounded with a tenderizing mallet or squeezed in roller that has points that break it up in a pattern that looks like square cubes connected in a lattice. This allows a cheaper grade of meat like top round to be tender enough to cut and chew when mechanically tenderized this way. Cube steak is frequently used for chicken fried steak.
This is just an educated guess, as I couldn't find a definitive answer either. I believe that flavorful, but tough cuts of meat were cut into cubes, back in the day, to tenderize them as they cooked, usually in some kind of liquid. Now, the tenderizing is done by perforating the meat, but the name remains.