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.
English contract law
The modern law of contract is primarily a creature of the industrial revolution and the social legislation of the 20th century. However, the foundations of all European contract law are traceable to obligations in Ancient Athenian and Roman law, while the formal development of English law began after the Norman Conquest of 1066. William the Conqueror created a common law across England, but throughout the middle ages the court system was minimal. Access to the courts, in what are now considered contractual disputes, was consciously restricted to a privileged few through onerous requirements of pleading, formalities and court fees. In the local and manorial courts, according to English law's first treatise by Ranulf de Glanville in 1188, if people disputed the payment of a debt they, and witnesses, would attend court and swear oaths (called a wager of law). They risked perjury if they lost the case, and so this was strong encouragement to resolve disputes elsewhere.