I wouldn't have been surprised to learn it were already named Lingua Mathematica, and I submit that as the best reason to give it that name (and not some other).
Based on my understanding, I think this is correct, but it sounds worse than common uses of the subjunctive I'm already familiar with (e.g. “if I were an Oscar Meyer weiner…”). Is it correct?
Note: I'm interested in prescriptivist English grammar here, not meaningless practicalities like being understood by people. There's no need to remind me that I'll be well understood only by saying “to learn it was.”
I am more confident of “I would not have been surprised if I were to learn it is already named Lingua Mathematica…” and not quite as much more confident in “I would not have been surprised were I to learn it is already named Lingua Mathematica…” which sounds extra hoity-toity.