In context, this seems to be a mash up of “(to know something) like the back of my hand” (to know a place very well) and “neck of the woods” (a region or locale in the country). The speaker was going to a party north of the city. When someone asked him if he knew how to get where it was being held, he said “Well, I know that area like the back of my neck”. Interesting thing is that he had never been in the area, but he had GPS. Of course, he might have been thinking that it was a “pain in the neck” to visit an area unfamiliar to him, or that neck and back are similar looking and sounding words, but who knows what lurks in the mind? Body parts, particularly the hands, are for some reason the source of many malaphors. I have posted several, including “I don’t know it off the top of my hand”, “I have it on the tip of my hand”, and the ever popular “we’ve got our hands cut out for us”. A big thanks to Joseph Newcomer for sending this one in!