In Czechia we have some interesting phrases about other countries:
It's a Spanish village to me - I don't understand it. (For example I don't know how to program, it's a Spanish village for me.)
He drinks like a person from Denmark - He drinks a lot of alcohol.
It appears many languages have an equivalent to this, and many like English, point to Greek with "It's Greek to me" - and the Greek say "it's Chinese to me" and apparently the Chinese say "it's heavenly script". Here's an interesting chart showing where many languages point for something incomprehensible. Source