In college we had students from all over the place, so when a Professor in one of my classes said as an aside, "it's all Greek to me," probably because he had written some math symbols that were squiggly Greek and he didn't actually know what he was writing, he paused and put Nick, our token Greek guy, on the spot and asked what people back home said in that situation. The reply was "it's all Chinese to me". Well, we had no shortage of Chinese guys in the classroom, so we asked them. "It's all Russian to me," was their response in unison. I guess my school wasn't hot stuff, because we didn't actually have a Russian, or maybe it was the quaint custom in those days to not invite our adversaries to learn secrets along with our students. But I bet they had some other language to blame, and so on, and so on, and eventually it would have circled back to "it's all English to me" if we had kept at it.