The shout comes from Cristiano Ronaldo's trademark goal celebration, in which he leaps, turns in the air and lands shouting Siu, a playful twist on the Spanish and Portuguese word for yes. Fans and broadcasters picked it up, and the stretched version became a chant in stadiums and a staple of football clips, edits and memes shared across social media. Because the sound is short, instantly recognisable and tied to scoring, creators still use it to signal confidence, victory or a moment that deserves a celebration.