Cristiano Ronaldo, the Portuguese footballer who has played for Manchester United, Real Madrid and Juventus, made the Siuuu celebration famous during his years at the top of world football. The shout comes from si, the Spanish word for yes, stretched out as he jumps, turns in the air and lands with his arms wide. Fans in stadiums began copying and chanting it back, and clips spread widely on social media and in football edits. It remains popular because the sound alone signals triumph, confidence and a goal scoring moment.