Definition & Meaning of "a pain in the neck"

What is the origin of the idiom "a pain in the neck" and when to use it?

The idiom "a pain in the neck" uses the metaphor of physical discomfort or annoyance in the neck area to express a sense of frustration or exasperation. It is used to convey the idea that the person or thing being referred to is causing significant inconvenience or annoyance, similar to a persistent pain in the neck.