The reference to the fall of the angels is drawn from pseudepigrapha.
British Dictionary definitions for pseudepigrapha
Pseudepigrapha
/ˌsjuːdɪˈpɪɡrəfə/
plural noun
1.
various Jewish writings from the first century bc to the first century ad that claim to have been divinely revealed but which have been excluded from the Greek canon of the Old Testament Also called (in the Roman Catholic Church) Apocrypha