The proof is in the pudding. This expression means that the best way to find out if something is good or successful is to test it yourself.

The Oxford Dictionary of Quotations claims this expression was first used in the early 14th century. As with many expressions, this one has changed over the years. People back then said it this way: the proof of the pudding is in the eating.

Knowing the full original version is important when explaining this expression. Also important is understanding the two main words in the sentence: pudding and proof.

First, pudding. You may ask, “What is that?” Well, the answer depends on whether you are using American English or British English.

In the United States, Canada and many countries in South America, “pudding” is a treat made with milk, eggs, sugar and flavoring like vanilla or chocolate.

However, if you order pudding at a restaurant in London and expect a soft, sweet dessert, you could be in for a big surprise. In Britain, pudding is a savory meat dish. In fact, the British would call our sweet dessert pudding a custard.

Now, the British do have sweet puddings such as their sticky toffee pudding and Christmas pudding. But they are solid puddings made with a lot of dried fruits. Again, nothing like an American milk-based pudding.

And their savory puddings are even more different. Centuries ago in Britain, people combined different meats, placed them into an animal membrane, or tissue, and then made a kind of sausage.

They covered the meat-filling with a soft shell made from flour and meat fat. Then they would cook the pudding by boiling or steaming it.

Like I said, the two puddings are very different. But it is this traditional English “pudding,” that gives us the expression: “The proof is in the pudding.” And that brings us to the second word: proof.

Today “proof” means something that shows that something else is true. A similar word is evidence. But centuries ago “proof” meant to test something. So we could say the expression this way: “The test of the pudding is in the eating.”

And now, another question. Why is testing the pudding important? Well, to answer this we need to go back to the main ingredient in the British pudding: sausage.

Centuries ago, there was no refrigeration to keep food cool and fresh. So meat would often go bad.

If you weren’t careful, you could get “botulism,” a food-borne sickness. And the root word of botulism, botulus, is the Latin word for -- you guessed it -- sausage.

So, testing the pudding was the only way to really know if the meat was still good to eat. So, that is the story of this expression. Now, let’s talk about when and how to use it.

The proof is in the pudding is very common. I would feel at home using it with an office supervisor, strangers or people much older than me. Other ways to say this expression are: “I’ll believe that when I see it” and “I’ll be the judge of that!” These are both a little more casual.

To best explain how to use it, I’ll give you a few examples. In this first one, a woman’s car won’t start. So, her friend is helping to fix it. Or is he?

A: And then after I connect this wire here … your car will be fixed.
B: Are you sure? That doesn’t look right.
A: Yes, I’m sure!

B: Well the proof is in the pudding. Let’s start it up!
B: Yeah, I didn’t think that was right. Here, give me the tools.

In this next example, a team leader is talking to a group of computer programmers. They have been working hard on a new product and are preparing to test it.

A: All right, team. This is it. We have written the program and designed the website. Tomorrow we run our first live test.
B: We have worked so hard! I’m sure it will work!

A: I know you’ve all worked really hard. But the proof is in the pudding. If it doesn’t work, be prepared to work over the weekend to fix it.