This is excellent advice, and I've seen it replicated as far back as Fowler's book on refactoring. Does the trail go further back than that?

I may be mistaken, but I actually remember Kent Beck saying it in his original TDD book. That was the thing that made me understand how refactoring can take the place of big design up front. The best part is that you only work on things that you need as opposed to wandering around changing every piece of code that you don't like ;-)