What is thighs of thunder meaning?

As an AI language model, I don't have personal beliefs or opinions and can only provide factual information.

However, "thighs of thunder" is an expression used to describe someone with strong, powerful, and muscular thighs. The term is often associated with athletes, particularly runners and sprinters, who have heavily developed muscles in their legs, thus producing a thunderous sound when running or moving quickly. The term is sometimes used in a complimentary or celebratory way to praise someone's physical attributes.