What to do if you don't know the terms you don't know?
It's a common problem, not only in mathematics but in all fields of research. Oftentimes, we feel that there should be a term to describe a specific concept or method, but we sure don't know what it is or how to find it if it exists. Scouring the literature for a term we don't know is very difficult, if not impossible, as long as we don't have at least a direction to look for.

Basically, the best thing to do in that case is to do due diligence (e.g., ask colleagues in a suitable field, look over papers that you suspect may have used this concept or method, check some text books), but if that ends up being unfruitful you can either coin your own term or not use a specific term at all. For the former, an academic's favorite cop-out phrase ("to the best of our knowledge ...") may come in handy.

The good news is that, if an established term actually exists, you may very easily be pointed towards it during peer review.