Here's from Wikipedia describing 1 Enoch:
The Book of Enoch is an ancient Hebrew apocalyptic religious text, ascribed by tradition to Enoch, the great-grandfather of Noah. Enoch contains unique material on the origins of demons and giants, why some angels fell from heaven, an explanation of why the Genesis flood was morally necessary...
The older sections (mainly in the Book of the Watchers) of the text are estimated to date from about 300–200 BC, and the latest part (Book of Parables) probably to 100 BC.
Various Aramaic fragments found in the Dead Sea Scrolls, as well as Koine Greek and Latin fragments, are proof that the Book of Enoch was known by Jews and early Near Eastern Christians...Authors of the New Testament were also familiar with some content of the story.
A large part of the cosmological strangeness of Hart's New Testament is when he draws attention, in either translation or footnote, to the influence of 1 Enoch and Jubilees upon the text. A great example comes from 1 Peter 3:19-20. Hart's translation:
Whereby [Christ] 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.
The text speaks of Christ, after his death, evangelizing "the spirits in prison." These imprisoned spirits are also somehow connected to Noah. Most modern readers, I expect, have no idea what this text is talking about. So Hart provides a footnote, sharing the story from 1 Enoch and Jubilees:
These are notoriously obscure verses, but the difficulty they pose is often exaggerated...This is because at this point the reference [about "the spirits"] is not to human beings who have died, but to angels or daemonic beings imprisoned until the day of judgment (they are also mentioned 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. The idea of a pre-cosmic fall of the Archangel "Lucifer" or "Satan" was a later development of Christian thought...; 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 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 SemyĆ¢zĆ¢; they not only became fathers of the nefilim, but taught their human wives to practice sorcery; and one of them, AzĆ¢zĆŖl, 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 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 upon 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 in 1 Enoch).
As mentioned by Hart in this footnote, the other two references to God casting these rebellious angels into prison are 2 Peter 2:4-5 and Jude 1:6:
And if God did not spare the angels who sinned, but rather cast them into Tartarus in bonds of nether darkness, held there for judgment, and did not spare the ancient cosmos, but preserved the eighth person, Noah, a herald of justice, having brought a flood upon the cosmos of the impious... (2 Peter 2:4-5)And the angels who did not maintain their own position of rule, but instead deserted their proper habitation, he has kept in everlasting chains under nether gloom for the judgment of the Great Day. (Jude 1:6)
So that's the story. Fallen angels, now chained in darkness, fathered the giants, the ghosts of which, after the flood, became the demons.
Somebody really needs to make this into a VeggieTales...