title: Why is the ! in Swift called an 'implicitly' rather than 'explicitly' unwrapped optional?
body: <p>The name of the <code>!</code> always confuses me: it's called an 'implicitly unwrapped optional'. However, what is implicit about it? Implicit means "implied though not plainly expressed." However, does not adding a <code>!</code> plainly express its purpose? Does not adding a <code>!</code> make it explicit what we are trying to accomplish?</p>