This sound comes from the Metal Slug series, SNK's long-running run-and-gun franchise that began in arcades in 1996. The games became famous for detailed pixel art, chaotic action, and exaggerated weapon audio, including the memorable shotgun blast. Online, the sound spread through gameplay compilations, retro game tributes, and meme edits that needed a short, instantly readable hit. It is still used because it delivers a very specific arcade feel that newer, more realistic gun sounds often do not.