As near as I can tell, polenta and corn mush are the same thing--just one is pretentious because it has an Italian name. I did a side-by-side using a tube of Trader Joes polenta and a tube of Yoders corn mush. The only difference is the polenta didn't mash quite as much when cooked in a skillet.
Unlike a museum in Atlanta which included maize in an Etruscan exhibit on polenta several years ago, I do know that the modern version of polenta was NOT used by the Etruscans since they didn't have corn (a New World food not introduced to Italy until 1650). The curators were kind of put off when corrected.
3 months ago