You see, the members of Congress and the colonies were well acquainted with the phrase ‘natural born subject’. Now, did NBC come from that common term, or from a translation of Vattel made 10 years after the Constitution?
Members of Congress were also familiar with the differences between the terms "citizen" and "subjects". Natural Born Subjects owed sole allegiance to the crown. Natural Born Citizens owe sole allegiance to the Republic.
From the Minor decision:
"Before its adoption the Constitution of the United States did not in terms prescribe who should be citizens of the United States or of the several States, yet there were necessarily such citizens without such provision. There cannot be a nation without a people. The very idea of a political community, such as a nation is, implies an [p166] association of persons for the promotion of their general welfare. Each one of the persons associated becomes a member of the nation formed by the association. He owes it allegiance and is entitled to its protection. Allegiance and protection are, in this connection, reciprocal obligations. The one is a compensation for the other; allegiance for protection and protection for allegiance.
For convenience it has been found necessary to give a name to this membership. The object is to designate by a title the person and the relation he bears to the nation. For this purpose the words "subject," "inhabitant," and "citizen" have been used, and the choice between them is sometimes made to depend upon the form of the government. Citizen is now more commonly employed, however, and as it has been considered better suited to the description of one living under a republican government, it was adopted by nearly all of the States upon their separation from Great Britain, and was afterwards adopted in the Articles of Confederation and in the Constitution of the United States. When used in this sense it is understood as conveying the idea of membership of a nation, and nothing more."