Earl of Sandwich sounds line a person that make such epic sandwiches they have been granted nobility. But it's actually the other way around. The 4th Earl of Sandwich John Montagu is the man who came up with the idea of stuffing some meat between two slices of bread. This invention is sometimes described as Britain's biggest contribution to the gastronomy.
Lord Sandwich was an avid gamer and was often too immersed in his card games to have time for meals. The meat filled bread solved conveniently his problems enabling him to dine at the gambling table.
There is also an island in Hawaii called Sandwich. Not because you can get some awesome sandwiches there nor is it made out of sandwiches, but because captain Cook named it after the Earl who had provided him with financial support for his admiralty. One could say that it's a sandwich made by a Cook.
So sandwich is just another food named after person without any deeper connection with the name and the actual food itself. In Finland we just call those as "voileipä" which translates to butter bread. There is also the term butty which apparently can be used in English which has the similar origin in "buttered bread". These both have expanded to mean all kinds of filled breads instead of just plain slice of bread with butter on it.