I have been thinking about this lately...
brimstoneSalad wrote:What if it was an ancient linguist playing a joke on the future?
Well, some ancient linguist making a fake Rosetta Stone convincing enough to fool modern linguists is highly implausible. If you try to produce a long meaningless text which looks like a language without knowing modern linguistics, chances are, your text will have statistical properties vastly different from a real language. That's why, if you claim the Voynich Manuscript is a hoax, you need to show an algorithm which a medieval person could use to generate such a hoax (matching statistical properties of a real language so closely). So far, nobody has done that. (That's not to say Voynich Manuscript is not statistically weird. Its first-order entropy is very similar to Hebrew, but its second-order entropy is very low, even lower than Hawaiian. But the question remains, which algorithm could a medieval person use to produce such a hoax?)
Now, if some ancient linguist was making fake glosses (translations of single words or short phrases), the chances of that getting accepted by modern linguists are a bit better, but it's still far from certainly fooling modern linguists. Constantine Porphyrogenitus made, as far as I know, one such fake gloss: claiming that "Croat" means "one who has a lot of land" in Slavic. He was obviously mistaken, there is no similar word with such a meaning in any modern Slavic language.
Now, whether some ancient linguist could fool modern linguists by making fake glosses from a language we know little about... It's hard to tell. The author of Ravenna Cosmography claimed that there are rivers in Pannonia called
Ira and
Bustricia. We have no idea which rivers those are. But we are pretty sure
Bustricia is a real river name, because it has quite an obvious etymology: it is related to Proto-Slavic *bỳstrъ meaning "quick". Now, whether there was a river named
Ira... It's hard to tell. What could the name
Ira mean? So, yeah, it is quite possible the author of Ravenna Cosmography made up a river name and fooled modern linguists.
I think that the study of names of places relies too much on the works of ancient linguists. Historical sources can be useful, sure, but it's primarily to dismiss false etymologies. The claim that the river name "Karašica" comes from the Croatian fish name "karaš" (crucian carp, from Latin "carassius") can be proven wrong by the early attestations of that name, such as "Karassou", containing a different suffix. But even without that, I think it should be obvious that etymology is unlikely. Before Gatski Kanal was built in 1875, Karašica was a lot faster, making it unlikely there were ever many crucian carps there. Furthermore, why would the first two consonants of many Croatian river names be 'k' and 'r', respectively (I call that "k-r pattern"), if those river names do not share the same root (or at least the same prefix)? The claim that "Poreč" comes from Croatian for "at the river" can be disproven by pointing that its ancient name, long before there were Croatians there, was "Parentium". But even without that, I think it should be obvious that etymology is unlikely. Which river would motivate it? Also, in the local dialect, Proto-Slavic *ě (found in Proto-Slavic word for river, *rěka) changed to 'i', rather than to 'e'. To claim that "Poreč" comes from Croatian for "by the river", one would need to invent that some different dialect of Croatian was once spoken there, which is an obvious ad-hoc hypothesis.
But, like I've said, I think the study of the names of places should rely less on the works of ancient linguists and more on mathematical methods. As I've written
my latest paper (there is an English summary
on my blog), I think I have proven by measuring the collision entropy of the Croatian language and doing birthday calculations that the probability of that k-r pattern occurring by chance is between 1/300 and 1/17. I think that proves beyond reasonable doubt that those river names share the same root, or at least the same prefix. Obviously, some ancient linguist confirming that would be excellent, but I think that even absent that, it is reasonable to believe my theory.