The Yale Law Journal's Pocket Part has made Jill A. Pryor, Note, The Natural-Born Citizen Clause and Presidential Eligibility: Resolving Two Hundred Years of Uncertainty, 97 Yale L.J. 881 (1988) available online. If you missed it, check out Jack Balkin's hysterical post, and for my prior take, check out this post.
Reading the Pryor note suggests to me that that the phrase "natural born citizen" had become a "term of art" by 1789 with both a core content and a zone subject to legislative determination. The core content is that "natural born citizens" must be persons who status as citizens accrues at birth: no one whose citizenship resulted from a subsequent event, such as naturalization can be a "natural born citizen" and all persons who were born of citizens on American soil must be "natural born citizens." The zone subject to legislative determination concerns the class of persons that can be added to the category. Possibilities include but are not limited to: (1) persons born of foreign parents on Amerian soil, (2) persons born of American citizens on Foreign soil, (3) persons born of mixed (American and foreign parents). The 14th Amendment handles category (1) and part of (3): hence all persons born on American soil are now "natural born citizens," but Congress has the power, through immigration law, to confer citizenship at birth to other groups, e.g., to category (2). If Congress does confer citizenship at birth, then "natural born citizenship" follows automatically--no further action is required. For reasons of constitutional clarity, predictability, and certainty, it would be wise for Congress to use the phrase "natural born citizen" whenever it confers citizenship at birth.
The difficulty with the phrase is that it is a lost term of art. First, "natural born citizenship" was a "term of art." "Natural born citizen" is not now, and probably was not in 1789 commonly used by ordinary speakers outside of specialist discourse (e.g., writings and other utterances concerning legal and political status among those learned in the law and political theory). (I base this conclusion on the information in the Yale note & could easily be persuaded otherwise.) The phrase is itself infelicitious--in the following technical sense, the reference of "natural born citizenship" is not derivable from the concatenated word meaning of the phrase. "Natural born citizens" are not citizens whose birth is natural. Indeed, the term natural makes a nonobvious contribution to the meaning of the phrase--apparently being a product of the sense of natural obligation in 17th and 18th century political theory. So "natural born citizen" was a term of art the meaning of which was fixed by specialist usage. The meaning of the phrase seems to have changed over time--originally referring only to citizenship acquired at birth by persons born of native parents on native soil and then extending to other forms of citizenship at birth that resulted from legislative acts. Second, the specialist usage that would have been familiar in 1789 is now lost--because the phrase is no longer in common circulation among the relevant specialists--immigration lawyers and poltical theorists.
Becuase "natural born citizenship" is a lost term of art, it appears "semantically opaque" to modern readers. We just don't know what it means. To determine the semantic content of the phrase, we need to recover the original meaning--the meaning the phrase had at the time of constitutional utterance. We look for public meaning, and discover that the division of linguistic labor in the late 19th century takes us to a specialist discourse. We examine specialist usage during the relevant period and recover the lost semantic content. It strikes me that this case of semantic opacity provides a wonderful example of what we might call the "inescapability of originalism." Without resorting to originalist investigation, "natural born citizenship" lacks meaning: the core insight of originalism, that semantic content is fixed at the time of utterance, is also the key to unlocking the puzzle of "natural born citizenship."
These remarks are very brief, and I urge you to read the Yale note for context and supporting evidence.