The expression “that's nuts” is an informal phrase used to convey surprise, disbelief, or incredulity. The origin of this phrase can be traced back to the metaphorical use of the word “nuts” to refer to one's head or mind. This usage dates back to the mid-19th century.
The word “nut” has long been used as slang to refer to one's head, and by extension, one's mental state. This can be seen in expressions such as “off one's nut,” which has been used since 1861 to mean “to be insane.” Similarly, one might say someone is “out of their mind” or “out of their head” to describe someone who is behaving erratically or illogically.
The metaphorical association between nuts and insanity likely stems from the idea that a person's mind can be as unpredictable and hard to crack as a nut. Just as it can be difficult to open a nut to reveal its contents, understanding or deciphering the thoughts and actions of a person who is mentally unstable can be equally challenging.
The use of “nuts” in the phrase “that's nuts” can be seen as an abbreviated form of these earlier expressions. When something is described as “nuts,” it implies that it is outrageous, absurd, or beyond rational comprehension. It is a way of expressing disbelief or astonishment at a situation or statement.
The phrase “that's nuts” is commonly used in informal conversation and is often accompanied by gestures or facial expressions to emphasize the speaker's incredulity. It is a versatile phrase that can be applied to a wide range of situations, from hearing a particularly unbelievable story to encountering a bizarre or illogical event.
Personally, I have often found myself using the phrase “that's nuts” in response to situations that defy logic or common sense. It is a succinct and expressive way to convey surprise and disbelief, and it has become ingrained in modern vernacular.
The expression “that's nuts” derives from the metaphorical association between nuts and one's head or mind. It is an informal phrase used to express surprise or incredulity at something that is outrageous or beyond rational comprehension.