I cant piece something together

So Doflamingo right, and everything with SMILE, I cant articulate a theory, but my curiosity is why would Oda attribute something so devious, with the word smile?

In the context of the story, laughing, joyboy, all of that, a former celestial dragon makes something called smile?

I dont have any dots to connect if there are, but does anyone else see what I am talking about?

Im curious why a story around laughing and fun, that Oda gave one of its most devious villains the word smile

In short, why is such a important word given to the villain.