In Hebrew we also say "It's Chinese" when we don't understand something.
Interestingly enough, I took the family to Greece just last month and explained to the children that in English, it is said that something sounds Greek if it cannot be understood. My oldest was wise enough to ask why, if Greek is the root of so many English words. I still don't have an answer for her!
Just a guess, but the Catholic Church relied on a Latin translation of the Bible. Accordingly, schools taught Latin as you needed it to understand the Bible and the Mass.
Those schools also taught Ancient Greek for advanced students to be able to read philosophy and portions of the Bible. This was useful if you wanted to be a priest, but otherwise it was just a pointlessly hard course for most students.
I had read that during the Roman empire there was a lot of Latin-Greek bilingualism, and that an educated person would be expected to know both, even in the western part of the empire. At some point that ceased to be the case and those places just got Vulgar Latin and the various Romance languages.
Thank you, I'm going to mention that possibility to the kids this evening. There are other oddities that they are familiar with regarding Biblical translations, such as Moses being depicted with horns.
Interestingly enough, I took the family to Greece just last month and explained to the children that in English, it is said that something sounds Greek if it cannot be understood. My oldest was wise enough to ask why, if Greek is the root of so many English words. I still don't have an answer for her!