The theory that most, if not all, New Testament books were originally written in Aramaic. (This theory is disputed in academia.)
We've had several questions that touch upon or are motivated by the Aramaic Primacy theory. As Wikipedia notes:
This view was popularised in the West by the Nestorian Assyrian scholar George Lamsa, but is not supported by the majority of scholars, either of the Peshitta or the Greek New Testament.
This tag should be used for questions about the theory or questions that are primarily motivated by the theory. Questions that should not be also tagged aramaic as this tag assumes that one and most experts would assume greek to be more appropriate.