This term dates back to the early 80's. The original phrase was "scratch your neck".
Etymology: a common practice among sophisticated women after being proven
wrong is to
scratch their necks, while looking off or away. This action is rarely done by arrogant people when proven
wrong. Because of that, This phrase is used to let them know what they need to do, since they are wrong.
Person 1: I use Vit B for my skin to make it
soft.
Perosn 2: For
soft skin you should try Vit E.
Person 1: Vit B is the oil I need for good skin THANK YOU
Person 2: WRONG, Vit B is water-soluble therefor not an oil, Vit E is an oil.
Person 1: Really!
Person 2: Yea, Really. Scratch your neck!(or
scratch your dirty neck)