Answer:
What is the word that even in plain sight remains hidden?
I run through hills. I veer around mountains. I leap over rivers and crawl through the forests. Step out your door to find me. What am I?
I wiggle and cannot see; sometimes underground and sometimes on a tree. I really don't want to be on a hook and I become a person when combined with “book”.
I am alive without breath and cold as death. I am never thirsty but always drinking.
I am the home for feathery animals.
It has no top or bottom, but it can hold flesh, bones, and blood all at the same time.