The idiom “you scratch my back and I’ll scratch yours” means that if you help me, I will help you in return. It is often used to describe a situation where two people or groups cooperate for mutual benefit. For example, “If you vote for me, I’ll support your bill. You scratch my back and I’ll scratch yours.”
The origin of this idiom is not very clear, but some sources suggest that it dates back to the early 1700s. It may have come from the British Navy, where sailors who had to whip each other promised to be gentle. Or it may simply refer to the fact that it is hard to reach some parts of one’s back and one needs someone else to scratch them.
