Origin of "lucky duck"

Please explain the origin and meaning of Lucky Duck

Just a guess, but many phrases only survive by virtue of a rhyming element - the "bees knees" is a good example. Clearly, in Lucky Duck, it's the luck that's important and the duck is thrown in for emphasis and rhyme. Many rhyming expressions come from Cockney English - apples and pairs for stairs is just one example of many.
Hope this helps!