Git noob here.
I know this is against the principal of \"distributed source control\" but I want to \"password protect\" certain development branches in my GIT repos
I don't think this is possible. It would make things like merging near impossible since git needs to know about the branches in order to make a merge. Consider the situation where one of your trusted developers merge something from the hidden branch to your main branch. Then a non-trusted developer tries to merge his changes -> how would you resolve the conflicts?
But it's simple to get what you want: just have a separate repository and use that as a "branch" since merging from a different repository is about as easy as merging a branch in the same repository.