Definition & Meaning of "slip somebody a Mickey (Finn)"

What is the origin of the idiom "slip someone a Mickey" and when to use it?

The origin of the phrase "slip someone a Mickey" can be traced back to the early 20th century in the United States. It is thought to be derived from the name of a person who was notorious for drugging unsuspecting individuals. Over time, the phrase became more widely used to describe the act of secretly administering a drug to someone with the intent of incapacitating or sedating them. It is important to note that the phrase may carry negative connotations due to the unethical and potentially illegal nature of drugging someone without their consent.