<Li> "Well, maybe not 2012, but 2013, surely ." </Li> <Li> "Maybe at least a gun barrel sticks out?" (repeating the gesture .) </Li> <P> The idiom is apparently derived from a centuries - old Scottish proverb, though some other references to pigs flying or pigs with wings are more famous . At least one appears in the works of Lewis Carroll: </P> <P> "Thinking again?" the Duchess asked, with another dig of her sharp little chin . "I've a right to think," said Alice sharply, for she was beginning to feel a little worried . "Just about as much right," said the Duchess, "as pigs have to fly ..."--Alice's Adventures in Wonderland, Chapter 9 . </P>

Where does the expression when pigs fly come from