I do not know the context. I speculate that it is a derivative of an old English expression "silly goose" which includes expressions like "you silly goose" or " I'm a silly goose" or "he's acting like a silly goose." Such references to a goose in English are usually pointing out that you did something silly or embarrassing and you are admitting that it was wrong and/or a mistake.

It comes from the expression "silly as a goose" or "a silly goose." Note that "silly" is much milder than "stupid." http://idioms.thefreedictionary.com/silly+as+a+goose