sanctum /sangkˈtəm/

1. (esp in the phrase inner sanctum) a sacred place
2. A (very) private room

sanctum sanctorum noun

1. The holy of holies, the inner chamber of the Jewish tabernacle
2. Any specially reserved retreat or room (informal)

• masteries
• mastering
• masterings
• master-joint
• master-joints
• master-key
• master-keys
• masterless
• masterliness
• masterlinesses
• masterly
• masterly inactivity
• master-mariner
• master-mariners
• master mason
• mastermind
• masterminded
• masterminding
• masterminds
• master of ceremonies
• master of hounds
• master of the horse
• Master of the King's Musick
• Master of the Queen's Musick
• Master of the Revels