A word by any other name ...

[Child of the 7th Age]

We could thus posit some sort of Babel myth in the Legendarium to explain why the languages are unrelated, although clearly this would impact on the Translator Conceit discussed in an earlier thread. That might involve a Rosetta Stone story.

Bethberry - Regarding Babel....you are closer to the truth than you know. On at least one occasion, Tolkien expressed a fondness for the debacle of Babel and the resulting dispersal of tongues. In Angles and Britons, the O'Donnel Lectures (published in 1963), while discussing English and Welsh, Tolkien praised the diversity of language with this comment: O felix peccatum Babel (Oh, lucky sin of Babel). I think he would have been delighted to see the conundrum we've got here!