Dock icons mislabeled

This has to be the weirdest problem I've had with my MacBook Pro. I first noticed the problem yesterday. Dock icons suddenly are mislabeled. For example: The icon for Messages gets the label for "Photos," which just happens to be sitting to the immediate right. The Photos icon reads "Pages," which is the app whose icon sits to the immediate right; and so on. Here's a screen shot—

If I click on the Messages app icon (labeled Photos), the Photos app opens. What the ... ? What can cause this problem, and how do I fix it? In the community, I've seen a couple of vaguely similar questions, but they all seem to be from 8, 9, 10 years ago and not exactly the same question.