OMG. *g* The Bacchus one? Bwah. The dryad one was sad. And the centaurs? Poor, poor Merlin.

Arthur is so much more educated than he lets on. Merlin doesn't really get to see many negotiations yet, but canon should give us more of that, or we should just write some of it. Because, you're absolutely right, Arthur knows more than several languages, and he would totally teach Merlin some stuff too.