Sometimes I think up really good titles and I just have to use them.
Crisis first showed up in the early fifteenth century, coming from the Greek word krisis, which meant the turning point in a disease or, literally, judgment. Specific, huh? It came to us by way of the Latin crisis because they just couldn’t have K for the K sound. Seriously, can we just go back to the K? Anyway, krisis comes from krinein, separate or judge, and before that it was the Proto Indo European krei-, distinguish or sieve. Apparently, in the early seventeenth century, people stopped using it for the disease meaning and started just being a turning point in general. No word as to how it got from judgment to there, though.
There are some other words we’re going to look at today, and it might seem a bit weird. The first is concern. Really! It showed up in the early fifteenth century meaning perceive or distinguish (hmm, distinguish…that seems familiar) as well as to refer to. It came from the Middle French concerner and Medieval Latin concernere, touch or belong to. That’s the figurative use of the Late Latin word concernere, sift like in a sieve—now I know I’ve heard that word before. That’s because concernere is a mix of the classical Latin prefix com-, with, which means to sift, but also to see or perceive and is related to krinein. I guess distinguishing something is separating it, like you separate stuff through a sieve, and when you’re distinguishing it, you’re referring to it in particular…it almost makes sense.
Finally, we also have discern. It showed up in the late fourteenth century from the Old French discerner, distinguish (there it is again!) and the classical Latin discernere, which just means discern. Dis- means off or away, so the word is “separate off”. It’s like really separating something out. And unlike the other words, its definition stuck with it.
TL;DR: Crisis is almost pure Greek, -cern is totes Roman Latin, but they originally meant the same thing (distinguish/sift). Which really has little to do with how we use them today.