Common law
The common lawso named because it was "common" to all the king's courts across Englandoriginated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066. The British Empire spread the English legal system to its historical colonies, many of which retain the common law system today. These "common law systems" are legal systems that give great precedential weight to common law, and to the style of reasoning inherited from the English legal system.
Common good
Against that background, the common good became a central concept in the modern tradition of Catholic social teaching, beginning with the foundational document, "Rerum novarum", a papal encyclical by Pope Leo XIII, issued in 1891. This addressed the crisis of the conditions of industrial workers in Europe and argued for a position different from both laissez-faire capitalism and socialism. In this letter, Pope Leo guarantees the right to private property while insisting on the role of collective bargaining to establish a living wage.