What is the origin of the idiom "out to lunch" and when to use it?

The origin of the idiom "out to lunch" is rooted in the concept of taking a break from work to have a meal. However, it has evolved to figuratively mean being absent-minded, disconnected, or not fully engaged in a situation. It is used to describe individuals who appear inattentive, unaware, or out of touch with reality. This idiom is typically employed when someone is being perceived as lacking focus, coherence, or understanding in a given context, often in a light-hearted or humorous manner.