Idolatro comes from the verb idolatrar, meaning "to idolize" or "to worship". It's a strong and evocative verb that goes beyond simply loving someone.
In this song, the singer uses idolatro to express an intense, almost reverent admiration for the woman he loves, elevating her to a status of profound importance. It's a powerful way to convey deep devotion and respect, making it a memorable and impactful word.
For four verses this plays like an ordinary love song. The woman in it has the sun in her hands and the moon under her feet, and she wears the stars: "Tiene el sol en sus manos" (She has the sun in her hands), "Y en sus pies a la luna" (And the moon at her feet), "En su manto de estrellas" (In her mantle of stars). Banda Los Recoditos hold the reveal until the chorus and then say her name flat out: "Se llama Guadalupe" (Her name is Guadalupe), "Y es mi Virgen morena" (And she is my brown-skinned Virgin).
Once you know, those opening images stop being flattery and turn into plain description, because every one of them is painted on the tilma that hangs in half the houses in Mexico. The song also tracks how she got there: "Es de España su venia" (Her blessing comes from Spain), "Ella impera otras tierras" (She rules other lands), "Y en la mía es una reina" (And in mine she is a queen), and then "Es la india más pura" (She is the purest Indian maiden), which is the whole argument of Guadalupe in one line. What she actually does for the singer is small and daily rather than grand: "Alegrías de mi canto" (Joys of my song), "De mis penas, la cura" (Of my sorrows, the cure). A hymn wearing the clothes of a love song, brass section and all, which is a fair description of how this devotion works.