"Pandæmonium" (in some versions of English "Pandemonium") stems from Greek "παν", meaning "all" or "every", and "δαιμόνιον", meaning "little spirit" or "little angel", or, as Christians interpreted it, "little daemon", and later, "demon" (thus roughly translated as "All Demons"); or it can be interpreted as Παν-δαιμον-ειον = "all-demon-place". It is the name invented by John Milton for the capital of Hell, "the High Capital, of Satan and his Peers", built by the fallen angels at the suggestion of Mammon at the end of Book I, Paradise Lost (1667). Book II begins with the debate among the "Stygian Council" in the council-chamber of Pandæmonium. The demons built it in about an hour, but it far surpassed all human palaces or dwellings; it may have been small, however, as the demons are described as shrinking from their titanic size in order to fit in.
It was designed by the architect Mulciber, who had been the designer of palaces in Heaven before his fall. In Milton, Mulciber is also the Roman God Vulcan.