Desterrado means "exiled" or "banished": forced away from a place or a person. In the song, "desterrado en cuatro paredes" evokes the feeling of being trapped and isolated within four walls, giving this unusual word a powerful emotional meaning.
“Pucho Loco” introduces a narrator living without much self-control: he drinks, smokes, spends his time wandering, and says, “no tengo miedo ya de morir” [I am no longer afraid of dying]. Death is always beside him, so he feels already committed to danger. The image is blunt and almost reckless: “descontrolado, un poco loco” [out of control, a little crazy]. He also mentions prison and freedom, giving the song the tense feeling of someone whose choices could lead him back behind bars.
Then the song turns toward lost love. From “cuatro paredes” [four walls], he remembers their past and says he is suffering far from the person he loves. The sharpest detail is the conflict between their families and identities: “tu papá fuera policía y yo un ladrón” [your father was a police officer and I was a thief]. That line makes the romance feel impossible, while “me esperan años lejos de ti y de tu amor” [years away from you and your love await me] brings the story back to prison, distance, and regret. The lyrics are rough and repetitive, but that suits the narrator: he keeps circling the same mixture of smoking, danger, guilt, and longing.