The phrase, "Natural Born Citizen" comes directly from Vattel's treatise, 'Law of Nations', which learned men of the day (especially the Framers) were very familiar with.
I've done quite a bit of searching on that phrase since Obama was elected, but have found no colloquial references for it. It was essentially a legal term that defined a precise condition of citizenship (as defined by Vattel).
As far as I know, it may have been coined by Vattel himself.
I'm almost sure that I ran across another reference to NBC by one of the Framers in my travels, but all of my saved research is on the hard drive of a computer that's now FUBAR. I don't recall offhand now where I read it, or who it was that mentioned it.