Please tell me you are using Git-SVN or Hg-SVN. Using bare SVN as a client hasn't been necessary in over a decade.
We'll be migrating to Git this year though so.
For reference, the codebase is over 20 years old, and includes binary dependencies like libraries. Makes it easy to compile old versions when needed, not so easy on the repository size...
It's inherently confusing to juggle different trees, and clearly you need some terminology for it. At least this one has become a bit of a standard.