Mug shot: A photograph of someone’s face especially one made for police records. The word ”mug shots” comes from the British slang word “mug” meaning “face.”
Photograph of a hooded inmate at the Eastern State Penitentiary in Pennsylvania which is considered the world’s first true “Penitentiary.” According to the Eastern State Penitentiary (now a U.S. National Historical Landmark and museum) website:
In order to encourage penitence – or true regret – in the hearts of criminals, inmates would spend their entire sentence in solitary confinement. On the rare occasion when an inmate left his cell, a hood was placed over his head to ensure his identity would remain anonymous. Ideally, no inmate would ever see the face of another inmate.