Armiño translates to "ermine," a type of weasel known for its pure white winter coat. It's a beautiful and somewhat rare word to encounter in song lyrics.
In "Hijo de la Luna," the word is used to describe the albino child born to the gypsy woman: "Blanco como el lomo de un armiño" (White like the back of an ermine). This vivid comparison highlights the child's striking and unusual appearance, making the word both memorable and central to the song's narrative.
A gypsy woman begs the Moon for a husband, and the Moon names its price: "Pero a cambio quiero / Del hijo primero que le engendres a él" ("But in return I want the first son you bear him"). She takes the deal. The baby arrives "Blanco como el lomo de un armiño" ("White as an ermine's back"), with grey eyes "en vez de aceituna" ("instead of olive"), and her husband does the arithmetic a jealous man does: "Este hijo es de payo" ("This son is an outsider's"). Then one line turns the folk tale into a crime report: "Se fue a su mujer, cuchillo en mano" ("He went to his wife, knife in hand").
Mecano wrote this in 1986, and Laura Pausini sings it on her covers album YO CANTO 2. The chorus keeps asking the Moon the same unanswerable question, "¿Qué pretendes hacer con un niño de piel?" ("What do you intend to do with a flesh-and-blood child?"), and the last verse answers it: the baby is left on the mountain, the Moon takes him, and that is why she swells full "porque el niño esté de buenas" ("because the child is in a good mood") and thins to a crescent when he cries, "para hacerle una cuna" ("to make him a cradle"). An explanation of the lunar phases, built out of one terrible bargain.