[JoeProBono]

"A submarine sandwich, also known as a hero sandwich, Italian Sandwich, sub, hoagie, torpedo or grinder amongst many regional naming variations, is a sandwich that consists of a long roll of Italian or French bread, split lengthwise either into two pieces or opened in a "V" on one side, and filled with a variety of meats, cheeses, vegetables, seasonings, and sauces.[1] The sandwich has no standardized name, and many U.S. regions have their own names for it;[1] one study found 13 different names for the sandwich in the United States.[2] The usage of the several terms varies regionally but not in any pattern, as they have been used variously by the people and enterprises who make and sell them. The terms submarine and sub are widespread and not assignable to any certain region, though many of the localized terms are clustered in the northeast United States, where most Italian Americans live.[3]"

"Grinder (Italian-American slang for a dock worker)—New England.[5] Called grinder because it took a lot of chewing to eat the hard crust of the bread used. In Pennsylvania and Delaware, the term grinder refers to a sandwich that has been heated."

[Dr. Sivana]

"A submarine sandwich, also known as a hero sandwich, Italian Sandwich, sub, hoagie, torpedo or grinder amongst many regional naming variations,

They forgot "Po' Boy". I am starting to see "grinder" pop up in northern Illinois. I am not convinced that it has anything to do with the hardness of the bread, especially as a meatball or sausage and pepper grinder properly made will saturate the bread with so much sauce, that the original hardness of the Italian bread is no longer an issue.

Grinder is of course, the correct term, as they existed before modern submarines.