Where Does The Name Forth Originate From?

I'm not sure who the first person was to start it but in Europe it was customary to name the first born sons of kings after themselves.  For example in England you had Henry, Henry the second (which in the U.S. We call Jr.), Henry the Third, Henry the Fourth, and so on.  If there wasn't a king but a queen, the first born daughter inherited the name.    By naming their offspring with their own name, they were showing the world that their kingdom had a powerful linage and would not die.  This was true not only in England, but in France, Spain and the Nordic countries, Russia and even in some Asian countries like China.

Asia country