But the angels transgressed this appointment. and were captivated by love of women, and begat children who are those that are called demons; —Justin Martyr, Second Apology V
Plutarch…says that the mythical narratives told as concerning gods are certain tales about daemons, and the deeds of Giants and Titans celebrated in song among the Greeks are also stories about daemons, intended to suggest a new phase of thought. Of this kind then perhaps were the statements in the Sacred Scripture concerning the giants before the Flood, and those concerning their progenitors, of whom it is said, “And when the angels of God saw the daughters of men that they were fair, they took unto them wives of all that they chose,” and of these were born “the giants the men of renown which were of old.” For one might say that these daemons are those giants, and that their spirits have been deified by the subsequent generations of men, and that their battles, and their quarrels among themselves, and their wars are the subjects of these legends that are told as of gods. —Eusebius, Preparation for the Gospel 5.4