1 Peter 3:18-20 (note: scholars believe this not by Peter, but by an anonymous Christian)
"For Christ also suffered – on account of sins, once and for all, a just man on behalf of the unjust, so that he might lead you to God, being put to death in flesh and yet being made alive in spirit, whereby he also journeyed and made a proclamation to the spirits in prison, to those in the past who disobeyed while God’s magnanimity bided its time, in the days of Noah when the ark was being fashioned, by which a few – that is, eight souls – were brought safe through the water... "
Commentarey:
At 4:6, the text speaks of “the dead” as having been “evangelized,” the language here is of Christ “making a proclamation” to “the spirits.” This is not to human beings who have died, but to angels or daemonic beings imprisoned until the day of judgment (mentioned also in 2 Peter 2:4-5 and Jude 1:6).
During the intertestamental period, before the “official” canon of Hebrew scripture was generally established for either Jews or Christians, among the most influential holy texts for both communities were visionary books such as 1 Enoch and Jubilees, which (among many other things) recount the apostasy and punishment of various angels and their offspring in the days after the expulsion of Adam and Eve, and the evils these angelic dissidents visited upon the world – the ultimate consequence of which was the flood, sent by God to rescue the world from the iniquity they had set loose.
In the flood narratives known to the earliest Christians, the only angelic rebellion was that of those “sons of Elohim,” or angels, who, according to Genesis 6:2, were drawn by the beauty of “the daughters of men” to wed them; and according to these texts the mysterious “nefilim” of Genesis 6:6 (understood as monstrous giants) were the children sired by these angels on human women.
According to 1 Enoch there were two hundred of these sons of Elohim, or “Watchers,” who abandoned God’s heavenly court, led by a Watcher called Semyaza; became fathers of the nefilim, and taught their human wives to practice sorcery; and one of them, Azazél, taught humanity how to make weapons, jewelry, and cosmetics (with predictably dire results). On being informed of these transgressions by four of his Archangels, God sent the Archangel Michael to imprison the celestial dissidents in the darkness below and to slay the nefilim; but the ghosts of the nefilim then became the demons that now haunt the world.
According to the book of Jubilees, the angels who became enchanted with the beauty of human women were angels of a lower order assigned to govern the natural elements and kinds of this cosmos. In that version of the tale, the celestial angels imprisoned these fallen cosmic angels in the dark below to await the final judgment, while the nefilim were driven to fall upon and kill one another. After the flood, however, the ghosts of the nefilim were still wandering the earth as demons under their leader, Mastema or Beliar (assuming these are the same figure). When God ordered these bound in prison as well, Mastema prevailed on him to allow a tenth of their number to continue roaming the world till the last day, so as to test humanity and punish the wicked; and thus Mastema comes to serve as “a satan” (that is, an Accuser) in this age.
The reference to Christ journeying to these spirits to make his proclamation to them seems to echo the account of Enoch journeying to their abode in order to proclaim God’s condemnation upon them (in chapters 12-15 of 1 Enoch).
So "Satan" was not originally a personal name as such, but rather a signifier of function, "the accuser" or "the adversary" – and Enoch seems to use this word as a collective noun, or rather as the term applied to evil-as-such, manifested in fallen angels.
