But Athenaeum is not just a synonym for a library (although it is used that way nowadays, of course). Athenaeum was originally the name of a school in Ancient Rome, and it was named after the city of Athens, which back then was regarded as the seat of intellectual refinement.
So for a library in Earthdawn to be called Athenaeum, it means Athens must exist (probably under its Ancient Greek name, Athēnai, or something similar).
It could have been a discrepancy, but after mulling it over I think it's actually not so far-fetched: the first traces of human presence in the Attic peninsula date back to at least the Neolithic era, which would place it right during the Fourth Age if I'm not mistaken. The prehistoric caves under the Acropolis could have been a Kaer, and the Pelasgic wall could be the ruins of the ancient city... And of course, in Earthdawn the whole region is actually part of the Theran province of Vivane.
So there you have it: we can surmise that there is a proto-Athēnai in the Vivane province that is already known as a place of knowledge, to the point libraries are already called Athenaeums
