1911 Encyclopædia Britannica/Concierge

CONCIERGE (a French word of unknown origin; the Latinized form was concergius or concergerius), originally the guardian of a house or castle, in the middle ages a court official who was the custodian of a royal palace. In Paris, when the Palais de la Cité ceased about 1360 to be a royal residence and became the seat of the courts of justice, the Conciergerie was turned into a prison. In modern usage a “concierge” is a hall-porter or janitor.