The word pandemonium, according to several online dictionaries, was coined by John Milton in his epic poem Paradise Lost. The word is said to be a mix of the Greek prefix pan-, meaning "across", Late Latin demon, meaning "evil spirit" and the Latin suffix -um, indicating that the word is a toponym. One meaning once ascribed to the word was "Hell"; in fact, that is the meaning that John Milton clearly ascribed to the word in Paradise Lost. And yet that meaning is not the meaning normally associated with the word today. In most cases, pandemonium refers to chaos. It also is seen as referring specifically to the noise associated with chaos and, in particular, the noise produced by large crowds.
Quite honestly, the name "place of all demons" appears a little strange. The name Demonium, translating as "place of demons", would appear to be more than sufficient to describe Hell. The addition of "all" or, even more perversely, "across" to the description seems to add virtually nothing to the alleged meaning "Hell". In fact, given the absolute pointlessness of the pan- prefix, the traditional etymology, on closer examination, begins to sound a bit like a folk etymology. If so, while it may be true that the highly educated John Milton used the word conspicuously as a reference to Hell, the word may actually have had etymological roots stretching much further back in time.
It is also rather curious that no one other than Milton appears to have ever used the word pandemonium as a reference to Hell. In all other cases I am aware of, the word appears to have been used to mean "chaos" or "chaotic noise". No one today, for example, ever says "You are going straight to Pandemonium!" It is as though the original "Hell" meaning was stripped from Milton's word and a new, more refined meaning was attached in its place. Could it be that a later writer rightfully regarded Milton to be a second-rate wordsmith and, while finding the name Pandemonium to be inherently alluring, simply rejected the meaning Milton gave the word and instead assigned it one of his or her own choosing, and that it was that subsequently assigned meaning that later users of the word eagerly embraced?
Of course, it is also possible that it was Milton, not some unidentified later writer, who stripped the word of its original meaning and intentionally gave it a novel meaning. Milton was, after all, a poet. That is exactly the kind of thing that poets do. Poets play with words. It is quite conceivable that Milton took a rarely used synonym for chaos and turned it into the proper name of a fictional city.
One must also wonder why a clever and highly educated wordsmith like Milton would have elected to coin what appears to be a poorly conceived toponym like Pandemonium and use it prominently as the name of Lucifer's city. Clearly Milton must have liked the unusual word for some reason or he would not have used it and would likely have used instead one of the many, well-established names for the underworld. Right?
The fact is that word meanings tend to expand rather than narrow over time. That is because poets and scholars like to use analogies. They take a word with a very specific meaning, such as the word key (i.e., "an object used to unlock a lock"), and use it in a new, analogical way (.e.g., as a reference to something that "unlocks" understanding, as in "key points or ideas"). Consequently, if we want to discover the original meaning of a word, it is often helpful to examine carefully its most narrow meanings.
Ignoring Milton's poetic use of the word, perhaps one of the most narrow meanings of the word pandemonium is "noise created by a chaotic crowd". Could that meaning possibly be demonstrated to be the original meaning of the word? The answer, I believe, is that it can.
One word that is very similar to pandemonium is the word pandemic. The word pandemic derives from two Greek words, the pan- prefix, meaning "across", and the word demos, meaning "the regions". Our modern meaning for the word pandemic, "a disease that infects people in many areas at the same time", clearly derives from the original, ancient meanings associated with the word's root and affixes.
Now, along with the word pandemic, another very important word that also can be seen to have derived from the Greek word demos is democracy. The ancient Athenian democracy involved the citizens from all of the demos, or regions, of Attica coming together to discuss important issues. Now, just as today, the discussions that were held in Athens were not always exactly stoic. When there were opposing views concerning important issues, tempers tended, as they often do today, to flare. And if there was a great deal of dissent, it is easy to envision the assembly quickly turning a bit chaotic and, well, noisy. In other words, a previously civil discourse could easily have degenerated at any time into utter pandemonium.
Finally, one should also take a long hard look at the word demon. The word demon today is generally understood to mean "evil spirit". It is believed, however, that the word in ancient times originally was simply a reference to any spirit, whether good or bad. But, as in the case of so many other words like it, the word demon, I believe, originally referred to something else entirely: the independent and often diverging concerns and desires expressed by the various demos, the regions, that met within the Athenian assembly. In other words, the word originally may have had more to do with attitudes (the spirits) of living people than it did with disembodied ghosts. And I also tend to suspect that the word's evil or bad connotation likely existed from the very first use of the word demonic.
Given the preceding, it would appear quite possible then that the word pandemonium may have, like the words pandemic and demon, had something to do with the ancient Athenian democracy. If so, then perhaps what Milton did with the word can be seen, not as somewhat questionable logogenesis, but rather as the inspired product of a scholar with more on his mind than merely placating a shallow desire to flaunt his knowledge of Greek and Latin.
The fact is that democracy has not always been so readily embraced as a political panacea as it often is today. Since the days of the Athenian democracy, people have often questioned whether democracy is truly a good form of government. Decisions made by the majority do not, after all, necessarily constitute decisions cautiously crafted out of sophia (Greek for "wisdom"). And participation by members of the uneducated working class, the idiotes, was not always welcome in the Athenian democracy either (hence the reason why calling someone an "idiot" was a huge insult, as it suggested that one was acting as though one was uneducated).
Perhaps Milton, being a man of letters, understood those biases quite well and was cleverly making a political statement of his own when he selected the name Pandemonium for Lucifer's city. Milton, in addition to being a poet, was, after all, a political philosopher, and he lived during a time of significant upheaval in England's political history. He, like his contemporary Oliver Cromwell, had no stomach for an absolute monarchy. But Milton did not embrace democracy either. Instead, he embraced the idea of a Platonic oligarchy in which the new republic of England would be governed, not by a monarch or by democracy, but rather by a council of philosopher statesmen, whose membership within the governing council would essentially be permanent.
We should also recognize that it is frequently from the madness of crowds that dictators arise. And that was, I think in Milton's own view, exactly what had transpired six years before he wrote Paradise Lost, when Charles II, riding on a wave of popular sentiment, returned to power. Consequently Milton would have had ample reason to give both the ideas of democracy and monarchy a black eye.
So is it possible that Milton was completely oblivious to the inherent linguistic relationship that existed between the word democracy and the name he proudly offered for Lucifer's capital? Given what I have just presented, I think one might perhaps have to be an idiot (pardon my Greek) to believe that he was. Thus, while Milton's use of the word pandemonium may be the first attested use, there is ample reason to suspect that he did not, in fact, coin the word, as is often claimed.
Curiously a possible Olin translation for pandemonium is "extension below related body, out of movement related after/above related, within original movement related". That translation appears to describe fairly accurately one common example of apparent chaotic motion: a pendulum swinging within another pendulum.