Rabbi of Berlin:
You raise a fair question. Why can’t we create new names? Obviously R’ Chaim’s psak has been previously mentioned so we’ll move along. According to the Sefer that this topic is about. on page 168, it quotes (in a footnote) that R’ Eliashiv, R’ Mordechai Eliyau and R’ Z. N. Goldberg there is seemingly no problem.
HOWEVER!!
1. The name is a Hashba on the child, what Hashba are you giving your child with this new name?
2. IIRC, The sefer differenciates and says that Parents used to have NEVUA as to what to name their child, but only have Siyata D’Shmaya now
3. It is Absolutely Ossur according to all to name your child a name which they will be ridiculed for having. How many people would like having the name “Ohr Zaruah”? It might sound beautiful to the parents, but I’d bet it would be a tough name for a kid to have.
4. This also explains why this is less of a question with the Yiddish names. Since the name has a Hashba, if naming Feige cause of Bubby Feige or Zundle because of great Uncle Zundle, so there is your Hashba. (Whether that Hashba is the one you want for your child or not is another story)
5. That is why the sefer suggests one asks a “Shayilas Chachom before naming, especially if naming a “new name”.