#7: Day Day?
One of the best-known events in World War II, and in the whole 20th century, is June 6, 1944: the Allied invasion of France, when thousands of Allied troops landed on the beaches of Normandy. It was the beginning of the eventual Allied victory and is commonly known as D-Day. But what does D-Day mean?

There are a few different theories and explanations floating around, but the most commonly accepted one is that the D also stands for “day,” meaning the full name is “Day Day.” Allied commanders, you did a terrific job winning the war. But you really need to work on coming up with better names for things.