While Professor Dhadphale's etymology for vekurañja <dvaikulajanya connects ñja with janya, I have observed another Sanskrit usage with jña that may be of some interest. The word svopajña is conventionally used for self-authored commentaries and one can see this word in numerous publications.  Offhand, I don't know how old this expression is, and I have not seen any traditional explanation of the word svopajña.  It seems to me that the component upajña in this word makes better sense with the verb upajāyate than with upajānāti.  So here we have a possible instance of jña in the sense of janya. Just an early morning thought.