Short shouted reactions like this one have circulated for years on gaming servers, forums and soundboards, where players trigger them live to comment on a round in real time. The CSS tag points to that Counter-Strike community culture of custom server sounds and quick chat reactions. Because the phrase is universally understood and the clip is only a couple of seconds long, it moved easily into video edits, streams and meme compilations. It remains popular as a fast, no-context-needed way to mark something as genuinely unbelievable.