Derrito comes from the verb derretir, meaning "to melt". It's a vivid and expressive word that paints a strong emotional picture.
In the song, the artist sings, "Que por eso' beso', mi niña, me derrito" (Because of those kisses, my girl, I melt). He uses this word to convey how completely overwhelmed and captivated he is by his love interest's kisses, emphasizing the intensity of his feelings.
"Dame Un Besito" is a love song about being completely captivated by someone. The singer can't sleep, can't stop thinking about her green eyes, and admits he has made mistakes but genuinely wants another chance.
The chorus keeps it simple: he just wants a kiss, over and over, because that is what makes him melt for her.
In the bridge he gets more serious, promising he is the one who truly loves her and asking her not to let the spark between them fade.