Answer:
What is so fragile that saying its name breaks it?
By the way, what never moves, wears shoes, sandals and boots, but has no feet?
What is pronounced like one letter, written with three letters. And belongs to all animals?
What is lengthened by being cut at both ends?
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.
You use it between your head and your toes, the more it works the thinner it grows.