If you were around a century or so ago, and you knew him well, you might call him Bill. On a legal document, William Sidney Porter. If you read any of his 300+ published stories, you knew him by his pen name: O. Henry. The name now commands a prestigious short story award, but more than anything, his work effectively trademarked a device: The twist ending, the literary tie that binds. When you or I try it, the reader calls it an O. Henry twist.