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.
Seventh Amendment to the United States Constitution
Beyond all question, the common law here alluded to is not the common law of any individual state, (for it probably differs in all), but it is the common law of England, the grand reservoir of all our jurisprudence. It cannot be necessary for me to expound the grounds of this opinion, because they must be obvious to every person acquainted with the history of the law.