Which president was nicknamed "Dubya"?

Which president was nicknamed "Silent Cal"? Which president was nicknamed "Ike"? Which president was nicknamed "The Gipper," from one of his movie roles? Which president was nicknamed "The Great Communicator"? Which president is called the "Father of His Country"? Which president was known as "The Great Emancipator"? Which president's middle initial "S" famously stood for nothing? What was Ulysses S. Grant's original first name?