Answers to this question assert that there is no difference in meaning between these two words. So they should be merged?
Collins Cobuild English Dictionary:
Nomenclature: The nomenclature of a particular set of things is the system of naming those things [formal]
Terminology: The terminology of a subject is the set of special words and expressions used in connection with it
My opinion is that we do not need both of these tags. I would say to keep "terminology" as it is more widely known/used than "nomenclature".