The origin of the word pileated comes from the Latin word, pileatus, which means capped. Another variation of the word, pileus, means a felt cap that doesn't have a brim. The word is usually used to refer to a bird's head.
When using the word pileated to describe a bird, it is referring to the feathers on the species pileum, also known as the crown. A male pileated woodpecker has a scarlet crown with feathers that stand up on top of the head.
When using the root pileus, the word can also refer to a person with a hat upon their head. Although pileated is used in other root forms, it is most commonly used to refer to sea urchins or species of birds.