A killer application (commonly shortened to killer app), in the jargon of technologists, has been used to refer to any computer program that is so necessary or desirable that it proves the core value of some larger technology, such as computer hardware, gaming console, software, or an operating system. A killer app can substantially increase [...]

From my research, this saying comes from the belly gunners during WWII.  Twenty-seven feet (nine yards) is the length of the ammunition belt they uses to protect their planes from enemy planes.  If you used the entire belt, then you shot the “Whole Nine Yards.”  However, using all your ammunition does not means that you [...]