Sepulcro is a poetic, formal word for a tomb or grave, making it more evocative than the everyday word tumba. In the song, Buika sings about the loneliness of living beside her mother’s grave, giving the word a deeply emotional and memorable context.
"Amor Eterno" is a grieving child talking to a mother who has died. It opens on a face in the mirror: "Me miro en el espejo y veo en mi rostro / El tiempo que he sufrido por tu adiós" (I look in the mirror and see on my face / the time I have suffered since your goodbye). The singer tries to force the memory away and can't, and admits "Prefiero estar dormida que despierta" (I'd rather be asleep than awake), because waking means remembering she is gone.
The second verse turns specific and guilty. "Hoy pienso que pude haber hecho más por ti" (today I think I could have done more for you) sits beside "La misma soledad de tu sepulcro" (the same loneliness as your grave), and the loss gets a place: "El más triste recuerdo de Acapulco" (the saddest memory of Acapulco). The chorus wishes her eyes had never closed, then promises "Tarde o temprano estaré contigo / Para seguir, amándonos" (sooner or later I'll be with you, so we can go on loving each other).