What does the idiom 'It's (all) Greek to me' express?

The Greeks say " it's all Chinese to me"

My mother and I were invited to a Greek wedding. Of course it was all in Greek and had an un usual ritual. My mother asked Nick what was going on, and in a thick accent he shrugged and said, "it's Greek to me" ☺️

I recall a classmate using the term during a high school science lesson, only to be clipped across the ear by our teacher who commented: "That's because it was discovered by Greeks, you ignorant pillock!" (it was during the '60s)

this reminds me of that player who always comments "another Greek word!"

Shakespeare's word

dana, by being Greek. this game sometimes can be easier.

Shellback, Also astrology, galaxy, e.t.c.

Planet is of Greek origin.

that was an easy one!