I believe a great deal is not known at all. Let me give a simple example.
Roots are in fact a common occurence in many languages.
However our current perception of the rules of conjugation or the existence of roots avoids a great corpus of meaning. It would seem to emerge that either our knowledge of the rules of conjugation has huge gaps or else that the idea of a root as the unit of meaning is not correct. Just some food for thought. I am attempting to rederive Biblical Hebrew in the hope of understanding Chazalian-Rashian Midrash as emanating from sound principles rather than Midrashic fancy. Rather the list tries to reconstruct through the use of lists an adequate theory of Biblical Hebrew that would encompass the rich nuances present in much Biblical commentary.