It is common in American restaurants to have a dish of conred beef. It is absolutely beef; however, I don't see any corn-like or something related to corn in this dish. Then, why do poeple call it corned beef? The same question comes up with prime ribs.
Usually, when talking about ribs, we think of babk back ribs, roasted pork with several ribs and special sweet sauce. However, prime rib is a cut of beef from the rib section and it doesn't come with any bone. I didn't recognize the difference until one day I ordered a prime rib in a restaurant and I expected to have baby back ribs. While the waitress devilered the dish, I finally knew I got it wrong.
As for corned beef, I've been asking some Americans but none of them know why it's call corned beef. Corned beef is basically pickled beef which is cooked by simmering. However, no corn is used during the process. The name "corned" is due to the coarse salt used in the pickling process. Here, "corn" means a small particle of something, though people use "grain" instead nowaday. Before refrigerator, people preserved meat by dry-cured in coarse "corns" of salt. Tranditionally, the beef was salted through the winter to preserve it and served on Easter in Ireland. Today, Irish-Americans and many others eat corned beef on St. Patrick's Day, which is Ireland's principal feast day, as a nostalgic reminder of their Irish heritage. Therefore, when having corned beef, you don't see corn or taste corn-flavor.