Ill be a monkeys uncle

Ill be a monkeys uncle is an older phrase which is referring to an expression of surprise or disbelief. It is based on past experiences with this kind of situation or person you are surprised at, because what has happened seems very unlikely. You never would of that something like this would have happened (it can be good or bad) and therefore say, well Ill be a monkeys uncle, because that is also nearly impossible but has happened regardless.