When you say something is a 'dud' you usually mean that it just isn't right. It's poor quality, a lemon. It's a great term, but occasionally we've found it to be a bit misused. Take, for instance, the example of the Milk Dud. These little candies are fantastic, and have passed the test of time. So, in this case, the term dud is a red herring, indeed!
If you grew up with Milk Duds, then you know exactly what we're talking about! These little gems are delicious and far from the failure their name proclaims them to be. And if you've never tried them, then you're certainly missing out! If we were you, we wouldn't wait one minute longer to get our hands on the most successfully misnamed candy around.