Directed Graph of Which Human Language Is Incomprehensible to Most People
languagelog.ldc.upenn.edu
languagelog.ldc.upenn.edu
So English -> "It's Greek to me." Chinese -> 《跟天书一样》
Others here. http://www.omniglot.com/language/idioms/incomprehensible.php
False. We say "está en chino" (it's in chinese).
In the comments to the Language Log post, a few German speakers describe variation in German as regional, and that may be true for the differences above.
Anyhow, the Omniglot table is here:
http://www.omniglot.com/language/idioms/incomprehensible.php
Arabs use Chinese ("Sini") as the archetype incomprehensible language.
It would be interesting to attempt to find historical references for them and see when they came into common use.