What ideas of the Constitution were original?

The Founding Fathers wrote the Constitution. They looked at a number of sources to develop the document. They wanted a federal government that had enough power to govern the people, but not too much power so that it could become abusive.
The Magna Carta was one document that was examined. In the Magna Carta, the nobles demanded that the King guarantee the people certain rights. The Magna Carta established the idea that the King doesn’t have unlimited power. While the King agreed to consult the nobles before making decisions, it did plant the idea that the King’s power could be limited. The Petition of Right was another document that was considered. The Petition of Right emphasized the idea that common people should have a voice in their government. The English Bill of Rights was a third document that was used. The English Bill of Rights guaranteed certain rights to the people. Free elections and protecting the rights of those who are accused of crimes are examples of rights people had.
The Founding Fathers also viewed the ideas of some of the leading thinkers of the 17th century. Baron de Montesquieu believed that people were able to govern themselves. He believed in the concept of separation of powers. In our government, there are three branches of government that have different jobs. No branch of government can do it all by itself.
John Locke was a thinker that the Founding Fathers studied closely. Locke believed that a government gets its power from the people. The job of government is to protect the rights of the people. There are certain rights that all people have and that can’t be taken away by the government. These include the right to life, liberty, and the pursuit of happiness. This view can be seen in the Declaration of Independence and in the Constitution.
While the Founding Fathers looked at other documents and considered the views of other philosophers, there are some parts of the Constitution that are unique. For example, the Great Compromise created a two-house legislature. In one house, there is unequal representation for each state. The larger states have more representatives than the smaller states. In the other house, there is equal representation for each state. Another example is the Three-Fifths Compromise. The Three-Fifths Compromise states that five slaves would be counted as three people when it came time to count the number of people living in each state.
Thus, while some ideas of the Constitution were drawn from other documents or from other philosophers, there are some aspects of the Constitution that are unique to it. Additionally, some of the ideas that came from other places had to be molded to fit our system of government as outlined in the Constitution.
https://m.landofthebrave.info/bill-of-rights-1689.htm

https://www.history.com/topics/united-states-constitution/constitution

https://www.ushistory.org/gov/2.asp