My family name is literally "son of a clean rock ("Clean rock" being my father´s name - Berghreinn). And my own name is an apt extension of this, the "Stone of Thor" - Thorsteinn. If you are familiar with Norse mythology, Thor was the God who controlled the sky and in a fit of rage could call upon a thunderstorm with the help of his mighty hammer called Mjoelnir. So, my fanciful own name could be interpreted as Mjoelnir, made out of clean rock - good material.