As far as the origin of the name 'Nine Inch Nails', Trent himself has said that it doesn't mean much, if anything. To paraphrase, he said that it sounded cool, abbrieviated well and didn't sound crappy after having heard it for a week. I really doubt that it has some Biblical connotation as that would be really cheesy and Trent seems to leave the cheese to his proteges, like Marilyn Manson and Filter.