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.
Law
However, the system became overly systematized—overly rigid and inflexible. As a result, as time went on, increasing numbers of citizens petitioned the King to override the common law, and on the King's behalf the Lord Chancellor gave judgment to do what was equitable in a case. From the time of Sir Thomas More, the first lawyer to be appointed as Lord Chancellor, a systematic body of equity grew up alongside the rigid common law, and developed its own Court of Chancery. At first, equity was often criticized as erratic, that it varied according to the length of the Chancellor's foot. Over time, courts of equity developed solid principles, especially under Lord Eldon. In the 19th century in England, and in 1937 in the U.S., the two systems were merged.