Or "Dumb-Ass Nigga Hoe" is a person who is often oblivious to the circumstances going on around them. Someone who doesn't pay a lot of attention, or is just generally stupid.
Girl 1: Oh my god, it's hot outside!
Girl 2: I love your flip-flops.
Girl 1: ... DANH.
Guy 1: How was your night?
Guy 2: Eh, it was ok. I spent it with Kate.
Guy 1: Whaaat? Don't tell me you slept with that DANH.
Guy 2: Why not?
Guy 1: I slept with her once. She tried to paint her nails while we were doing doggy-style.