it was the book of Samuel I believe. I'm not sure if his fallen angelic history was kept in all the different bibles used by different but similar religions. I was unsure of the religious leanings ( difference between Catholics and southern Baptist, same god, different trappings) of the kids book that I was given. However on some speculative t.v shows about giants and their angelic roots Goliath is mentioned a lot.
They varied, didn't they? I mean one Egyptian Giant Nephilim that was 7(?)ft tall had extra digits. Weren't others of different Heights? Like OG was 12 to 14 feet tall and handsome, I believe? And some were described as having extra rows of teeth or being "Lion like men." I don't know what they mean by Lion like, but when it said David and his mighty men killed a few in the snow, I wonder if it means they were just fierce or looked like the middle eastern version of X-men's sabre tooth.