Authors get asked all the time about the source of their ideas and there’s never a simple explanation. A fragment of conversation, a fleeting glimpse of the unconventional, an unexpected sequence of events, and suddenly the writer’s mind is asking, “What if…?”
The idea won’t be original. There are basic themes that have regularly reappeared throughout literary history. It’s a given that whatever one chooses to write about has probably already been written by someone else. What will make the story unique is not the idea but how it is developed by a particular author.
In his first contribution to the “Writer Unboxed” blog, Donald Maass says, “Originality can come only from what you bring of yourself to your story. In other words, originality is not a function of your novel; it is a quality in you.”
There is no better way to say it.