be so

be so

To be able or permitted to do something. This construction is mainly used for emphasis in short sentences that typically end with "so" or follow "so" with a verb. A: "You aren't allowed to have sweets this early in the day." B: "I am so! Mom said I could, just this once." A: "You guys aren't allowed to be here this late!" B: "We are so allowed! Let us in!"
References in classic literature ?
Consequently, I am the more surprised that YOU should be so cheerful.