What is the origin of the idiom "raving mad" and when to use it?

The origin of the idiom "raving mad" can be traced back to the Middle Ages. The word "rave" originally meant to wander deliriously or speak irrationally, and "mad" referred to mental illness or insanity. Over time, the phrase "raving mad" emerged as a way to describe someone who was wildly irrational or displaying symptoms of insanity. This expression can be used to describe someone who is excessively excited, acting in a wild or frenzied manner, or displaying irrational thoughts or behavior.