Calavera literally means "skull". It's an intriguing and somewhat unexpected word to find in a romantic song, making it memorable.
In the lyrics, the line "Pronto destiñó y se vio la calavera" (Soon it faded and the skull was seen) suggests that beneath a facade of peace (the white flag), a deeper, perhaps more intense or even dangerous truth was revealed. It adds a layer of edgy romance and mystery to the song's narrative.
India Martínez turns a chance hookup into pure euphoria here. The story opens mid scene: "Se cerró la puerta del local" [The door of the venue closed], and instead of panicking, the two people locked inside fall for each other on the spot. They don't need the usual trappings of a big night out. "No necesitamos, ni champán, ni tusi" [We didn't need champagne, or tusi], because "Nos bastó con las burbujas del jacuzzi" [the bubbles from the jacuzzi were enough]. It's a song that leans all the way into being silly about love, and it earns it.
The second verse gets cheekier. "La bandera blanca no sirvió de mucho" [The white flag didn't do much], and soon "Pronto destiñó y se vio la calavera" [It soon faded and the skull showed], lines that read like a private joke about giving in completely to someone. By the end they've stopped being two people and become one: "Pasamos de ser tú y yo a ser solo uno" [We went from being you and me to being just one], with the morning after described like something out of a fairy tale: "Y fue de diamantes nuestro desayuno" [And our breakfast was made of diamonds]. She insists the water in that jacuzzi "era bendita, bendita locura" [was blessed, blessed madness]. Cheesy on paper, but sung with this much joy, you believe her.