1 Enoch 6:1-2

1 And it came to pass when the children of men had multiplied that in those days were born unto them beautiful and comely daughters. 2 And the angels, the children of the heaven, saw and lusted after them, and said to one another: 'Come, let us choose us wives from among the children of men and beget us children.' 3 And Semjâzâ, who was their leader, said unto them: 'I fear ye will not indeed agree to do this deed, and I alone shall have to pay the penalty of a great sin.' 4 And they all answered him and said: 'Let us all swear an oath, and all bind ourselves by mutual imprecations not to abandon this plan but to do this thing.' 5 Then sware they all together and bound themselves by mutual imprecations upon it. 6 And they were in all two hundred; who descended ⌈in the days⌉ of Jared on the summit of Mount Hermon, and they called it Mount Hermon, because they had sworn and bound themselves by mutual imprecations upon it. 7 And these are the names of their leaders: Sêmîazâz, their leader, Arâkîba, Râmêêl, Kôkabîêl, Tâmîêl, Râmîêl, Dânêl, Êzêqêêl, Barâqîjâl, Asâêl, Armârôs, Batârêl, Anânêl, Zaqîêl, Samsâpêêl, Satarêl, Tûrêl, Jômjâêl, Sariêl. 8 These are their chiefs of tens.

Date: 200-50 B.C.E.
* Dates are based on scholarly estimates

Lactantius Divine Institutes 2.15

When, therefore, the number of men had begun to increase, God in His forethought, lest the devil, to whom from the beginning He had given power over the earth, should by his subtlety either corrupt or destroy men, as he had done at first, sent angels for the protection and improvement of the human race; and inasmuch as He had given these a free will, He enjoined them above all things not to defile themselves with contamination from the earth, and thus lose the dignity of their heavenly nature. He plainly prohibited them from doing that which He knew that they would do, that they might entertain no hope of pardon. Therefore, while they abode among men, that most deceitful ruler of the earth, by his very association, gradually enticed them to vices, and polluted them by intercourse with women. Then, not being admitted into heaven on account of the sins into which they had plunged themselves, they fell to the earth. Thus from angels the devil makes them to become his satellites and attendants. But they who were born from these, because they were neither angels nor men, but bearing a kind of mixed nature, were not admitted into hell, as their fathers were not into heaven. Thus there came to be two kinds of demons; one of heaven, the other of the earth.

Date: 300-310 C.E.
* Dates are based on scholarly estimates