What is the origin of the idiom "cheap shot" and when to use it?

The origin of the idiom "cheap shot" can be traced back to sports, particularly boxing. It originated in the early 20th century and referred to a punch or blow that was considered unsportsmanlike or delivered when the opponent was unprepared or defenseless. Today, it is commonly used in various domains to describe actions or remarks that are perceived as unfair, disrespectful, or taking advantage of someone.