Once' is a common word used in the beginning of many fairy tales. It is used to introduce the story and set the scene for what is to come. The word 'ONCE' is a four letter word that is commonly used to open fairy tales. It is used to introduce the story and create an atmosphere for the reader, allowing them to imagine what is about to happen. This word is often used to start off a magical journey that will take the reader on a journey of adventure and discovery.