It’s all in the Book of Enoch, which predates Genesis and was retrieved from Ethiopian Copts who had an oral tradition which included this book. It talks of giant angels who came to live among the normal humans, but I don’t think they used the name humans in the scripture : )
Just for the record, I think you’d have a hard time proving The Book of Enoch predates Genesis. Enoch properly belongs to a class of writing known as “pseudepigrapha” meaning it is a work that has a famous name attached to it but no actual evidence that they are the author. That being said, it is an interesting read. There is even a short quote in the Epistle of Jude in the New Testament.