But I've never even been to Olympus! Zeus is crazy!" Chiron and Grover glanced nervously at the sky. The clouds didn't seem to be parting around us, as Grover had promised. They were rolling straight over our valley, sealing us in like a coffin lid. Er, Percy ...?" Grover said. "We don't use the c-word to describe the Lord of the Sky.
"Percy Jackson and the Lightning Thief". Book by Rick Riordan, May 1, 2008.