Risa

It's already one of several planets that are identical to earth and have a history that parallels our own. The idea that planets in different solar systems would form as perfect copies of each other, and that they would both independently evolve humans, and those humans would form identical cultures that diverge only enough to create a 20th century Rome, that's a level of ridiculous implausibility that seems more like something you'd find in Hitchhiker's Guide to the Galaxy.

By comparison, the fact that they also developed modern English seems like a far more logical possibility, given that they are starting with copies of the same cultures and presumably the same linguistic roots more or less. And the word play itself might actually have been intentional, making it the least implausible part of the whole thing.