The pull up warning comes from the ground proximity warning systems fitted to commercial airliners such as the Boeing 737, where it alerts pilots to climb immediately when terrain or an unsafe descent rate is detected. Aviation enthusiasts and flight simulator players helped bring the sound online, sharing cockpit recordings and recreations that made the two-word command instantly recognisable beyond aviation circles. It remains popular because the warning is short, unmistakable and tied to a real life-or-death decision, so even viewers with no flying experience understand the danger in under a second.