Definition & Meaning of "milk the bull"

What is the origin of the idiom "milk the bull" and when to use it?

The phrase "milk the bull" may have originated from the idea that bulls are male and therefore cannot produce milk, making the act of milking a bull pointless and impossible. This phrase is used to describe a situation where someone is attempting to do something that is impossible or to try to extract something from a situation or person that is not possible.