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 school
A common school was a public school in the United States during the 19th century. Horace Mann (1796-1859) was a strong advocate for public education and the common school. In 1837, the state of Massachusetts appointed Mann as the first secretary of the State Board of Education where he began a revival of common school education, the effects of which extended throughout America during the 19th century.