Two farmers are standing in a field, watching some heavy, black clouds roll in swiftly from the north. The first farmer says, “Looks like we might get some rain.” The second farmer says, “Well, that’s a no-brainer.”
This is an example of the phrase in use. What the second farmer means to say is that what the first farmer said is obvious. A no-brainer means that there is very little thought required to find a conclusion or solution to a problem. In other words, no brain is required to come up with the answer because it is very simple.
When people began to say “no-brainer” is unclear, but it can be traced back to around 50 years ago. It is an expression that has been used in all types of popular media, including books, newspapers, on television, and in movies. No one knows the origins; it is just one of those funny, little expressions that has become a part of the English language.
Sometimes “no-brainer” is used as a phrase that will make a task seem easy. You can say that adding one plus one is a no-brainer, when in fact a brain is required. You can also say that doing laundry for the whole family is a no-brainer, but a lot of effort is needed to accomplish the task. Your grandma can claim to have a no-brainer recipe for making a soufflé, but everybody knows that they are hard to get just right. Grandma just wants to let you know that if she can do it, you can do it.
It can also be used to imply that a question is stupid. If someone is learning how to cook, they may ask how to make mashed potatoes. The answer can be that, “It is a no-brainer, because most everybody knows how to make them and it is an easy thing to do.” If you have never done a simple task, it is not simple to you – it is not easy and will require your attention and thought. Of course, after having made mashed potatoes 100 times or so, it becomes a no-brainer for you as well.
Occasionally, it is used to call a person stupid. A very young girl might say that butterflies come from caterpillars and be quite proud of her newfound knowledge. Her older brother might say, “That’s a no-brainer, duuuuhhh.” Sadly, the big brother isn’t very encouraging in this example, but it does give you an idea of its many variations.