After Atreyu loses Falkor he wanders through the broken remnants of Fantasia without purpose, and ends up coming across the man-mountain known as The Rock Biter. Buuuuuuuuut unlike the jovial stone man from earlier in the movie, The Rock Biter has become a real downer. Before, The Rock Biter's biggest worry was that his snacks were not as tasty as they used to be (losing interest in things you once enjoyed is a classic symptom of depression and the passing of The Nothing). But by the time Atreyu catches up with him, Ol' RB sounds like that one Bukowski-lite philosophy major friend of yours who always asks you to punch him when he gets drunk.
The Rock Biter is literally just sitting on the beach staring at his hands, lamenting that they were not strong enough to save his friends from The Nothing. "Such strong hands..." he keeps intoning, while his giant rock tricycle sits next to him, like the memory of a childhood lost. Maybe in another movie, Atreyu would have given him a rousing speech about determination and never giving up hope, but The Neverending Story don't play that. Instead The Rock Biter just straight up admits that he is going to sit there and wait to die, spending his final moments regretting the futility of his life. Why is this happening? In a movie for children!?
Where other fantasy movies could have pitted out heroes against an evil wizard, or an army of orcs, but The Neverending Story just really goes for it and throws the boys up against the eternal, and very real terror of non-existence. Pondering the questions of what happens when we die and the true nature of being, is generally left to insufferable college students, but the makers of The Neverending Story clearly thought the kids could take it. I'm not sure we could.
Calling it "The Nothing" makes the existential horrors of entropy and non-existence certainly seem much more like a fantasy beast to be vanquished. But in the end, all of Fantasia spends the entire movie running from the inevitability the void. It even tries to gussy it up as a bunch of beautiful, colorful clouds, but as just about every character in the movie points out, The Nothing is simply a wave of despair that drains life of all joy before rendering it meaningless by simply wiping it from reality. Never before has the concept of a genocidal warlock, or rampaging army seemed so pleasant. At least at the end of the day, they can be defeated. The Neverending Story made sure that a whole generation of children were ultra-aware that each day is just one closer to death. No wonder antidepressant use has been on the rise for decades.
In the end, to save all of Fantasia, Bastian simply has to give the Childlike Empress a new name, despite the fact that it seems like she never had one to begin with. As all of Fantasia succumbs to the unstoppable roll of entropy, Bastian, who has just had a deeply surreal and psychologically questionable quest through a dying world, just seems to shout out the first thing that comes to mind. Rushing to the attic window in a fit of dramatic (if nonsensical) fever, Bastian shouts the name out to the world:
Why giving the Childlike Empress a name could save Fantasia is not very clear, but why Bastian decides to name her something he must have read off the back of a bitchin' van is even more mysterious. C'mon, even by geek standards, Moonchild is a pretty embarrassing name. It's easy to think that maybe Bastian is just a lovable, but misunderstood nerd who would get along with his bullies if they'd give him the chance, but man, he has the opportunity to name his own demigod, and he totally biffs it. It's possible that this was his deceased mother's nickname back in the 70s or that it was more of a word salad situation like when someone has a stroke. But far more likely, Bastian is simply a deeply disturbed, deeply dorky young man.