Klein writes that the meaning of chaos and confusion is only from Modern Hebrew, whereas the original (i.e. post-biblical) meaning was "pestilence". He provides the following etymology:
Greek androlempsia, for androlepsia (=seizure of men in reprisal of the murder of a citizen abroad), compounded of aner, genitive andros (=man), and the stem of lambanein (=to take).
Andros as "man" should be very familiar as the root of words like android and anthropology, and the second half of the word, "-lepsia" also appears as "take, seize" in the word epilepsy, literally "a seizure". (Even-Shoshan proposes an alternate etymology: androloimos - "plague, annihilation". However, I have not been able to find any source for this, or even any mention of this Greek word anywhere).
The connection between Klein's definitions and etymology of androlomousia is somewhat confusing. First, what does pestilence have to do with androlepsy, and second, what do either have to do with confusion and chaos?
Regarding pestilence, I haven't found a source that explicitly describes andralomusia as such. It has a much more general sense in the midrashic sources that I've seen, such as this quote from Vayikra Rabba 23:
אמר רב שמלאי: כל מקום שאת מוצא בו זנות אנדרולומוסיא באה לעולם והורגת יפים ורעים.This midrash is discussing the flood, and so isn't referring specifically to pestilence, but general disaster and catastrophe. The additional note of killing "the good and the bad", fits nicely with the concept of androlepsy, where citizens were seized (and killed) regardless of their guilt. This type of situation, whether the actual example of androlepsy, or the analogous divine punishments mentioned in the midrash, besides being horrific, was surely chaotic as well. So we can see how the word took on its more modern sense.
Rabbi Simlai said: every place where you find lewdness, androlomusia comes to the world, and kills the good and the bad.
In current spoken Hebrew, androlomusia is not used very frequently. It's a bit antiquated - maybe even ostentatious. Israelis prefer the much shorter balagan בלגן. I hope this put an end to the confusion...