guideline

Use a name that indicates the kind of problem the exception represents.

Invalid_Name: exception;
Stack_Overflow: exception;

rationale

Naming exceptions according to the kind of problem they are detecting enhances the readability of the code. You should name your exceptions as precisely as you can so that the maintainer of the code understands why the exception might be raised. A well-named exception should be meaningful to the clients of the package declaring the exception.