What does Cristiano Ronaldo's goal celebration mean?

When Cristiano Ronaldo scores goals, he usually marks them with a particular celebration. So, what, if anything, is the meaning behind it?

What does Cristiano Ronaldo's “siu” mean?

Cristiano Ronaldo: Di striker don chop fine from Uefa for im goal

Cristiano Ronaldo: Why does Juventus star always do same

Explained: Why are tennis fans shouting Cristiano Ronaldo's Siiu

Cristiano Ronaldo gives Alejandro Garnacho permission to do iconic

Chronology of Cristiano Ronaldo Told Through His Goal Celebrations

The story behind Cristiano Ronaldo's iconic 'siii!' goal

What does Cristiano Ronaldo's goal celebration mean?

What Cristiano Ronaldo's new goal celebration meant after ditching