Writers get their inspirations from many places. It could be a real-life incident that happened to them or that they read about, or maybe previous literature. Get more than one writer involved, and you've got multiple inspirations. Small details are added to flesh out the story, and those details may have come from somewhere completely different. Stories are changed, added to, and sometimes improved as they move from book to movie to TV spinoff. And it's fun to find out how far an idea traveled to get on our TV screens.
I must admit that I expected something supernatural when I first read the prophesy.
Macbeth shall never vanquished be until
Great Birnam Wood to high Dunsinane Hill
Shall come against him
Tolkien's disappointment became Treebeard, and possibly Groot as well. That itself could become your inspiration for a new story- if you don't see what you want in pop culture, write it yourself!
Now that's a story worth looking up! Read about 28 of the inspirational origins of what you see in movies and TV, from the main story arc down to the smallest details, coming from different sources, at Cracked.