1.) Onomatopoeic representation of exhaustion or sudden sleep.
2.) Used to verbally escape from answering questions, or direct accusation by feigning sleep.
TIM: Bill, are you awake enough to go to the movies?
BILL: Nert (sleeps)
JILL: Jane, is this your bloody knife in the bathtub?
JANE: Well...I...NERT (feigns sleep)