1667, Pandæmonium, in "Paradise Lost" the name of the palace built in the middle of Hell, "the high capital of Satan and all his peers," and the abode of all the demons; coined by John Milton (1608-1674) from Greek pan- "all" (see pan-) + Late Latin daemonium "evil spirit," from Greek daimonion "inferior divine power," from daimōn "lesser god" (see demon).
Transferred sense "place of uproar and disorder" is from 1779; that of "wild, lawless confusion" is from 1865. Related: Pandemoniac; pandemoniacal; pandemonian; pandemonic.
*dā-, Proto-Indo-European root meaning "to divide."
It forms all or part of: betide; daimon; Damocles; deal (v.); deal (n.1) "part, portion;" demagogue; demiurge; democracy; demography; demon; demotic; dole; endemic; epidemic; eudaemonic; geodesic; geodesy; ordeal; pandemic; pandemonium; tidal; tide (n.) "rise and fall of the sea;" tidings; tidy; time; zeitgeist.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dati "cuts, divides;" Greek dēmos "people, land," perhaps literally "division of society," daiesthai "to divide;" Old Irish dam "troop, company;" Old English tid "point or portion of time," German Zeit "time."