"Suavecito" -- why masculine-form?

I know there’s a good reason why the word in the title of this song about a girl takes the masculine form – I just don’t know what it is.

Is it that, in this word, (a noun formed from an adjective with a diminutive ending,) the “masculine” ending is not representing the gender of the person thus described, but rather the “masculine” quality of suavity? Or what?

I’ve just always wondered, but it’s been awhile since high school Spanish.

I guess it is because it refers to “feeling”, which in Spanish is a masculine word (“sentimiento”).