Coined by David Brin in the superb second Uplift Trilogy. Brin thought Hmm, we already have Dyson Spheres which are in themselves pretty much impossible to build, so why not create something even more outrageous and yet cool; A Dyson Sphere with a complex surface that further increases the already gargantuan living space.
The glossary of Heaven's Reach contains:
Criswell Structure - Fractal shells designed to surround small red suns, utilising all light energy. The fractal shape allows maximum possible "window area", unlike a simple Dyson Sphere.