Store is Open
Odds and Ends
Yogurt as far as the eye can see
10 2, 4:35pm
the expression isn't about someone who understands all languages. It's just that Greek or Chinese looks or sounds gibberish and completely ununderstandable to some people, so when they say it's Greek or Chinese they just mean to say they don't understand what's written or said.
Anyway, if you want to find a source, here's some starting point.
And for what I understood, a group Proto Indo European languages are seen as the 'parent' of all we speak from Europe to South Asia. Plus all countries where one of these languages is the default nowadays due to the colonial era. I guess that covers about 75% of the population of the world.