Well there is the word "citizen", which doesn't come from English Common Law. The correct word for English Common law is "subject."
Then there is the fact that the word "citizen" actually comes from Switzerland. Here is etymology online for you to look at.
But probably the most compelling piece of information is this:
The etymology suggests that the word "citizen" was already in use in English before the American (or French) Revolution. Britons used the word "subject" because they had a monarchy. Americans wanted to do away with monarchy so they adopted the word "citizen." They could have used "freeman," but the assumption was that everyone was now free (and the uncomfortable reality was that not everyone was). Was it really likely that the Framers threw out their whole inherited system of laws when they adopted one word in place of another? Or did they simply replace "subject" with citizen?
I saw one of the videos that Mike Zullo made for Joe Arpaio. It's not very convincing. Politicians don't release personal documents unless they have to, so there may be no big secret at all. There may or may not be other secrets in other documents that they also don't want you to see, but their unwillingness to make something public is the rule, not the exception.