The word 乌龟 (wūguī) is formed by combining two distinct characters, each contributing a key piece of meaning to create the specific concept. The first character, 乌, originally depicted a crow and carries the core idea of "black" or "dark". The second character, 龟, is a pictograph that visually resembles the shell and shape of a turtle. When combined, they form a descriptive compound: a "dark/black turtle", which accurately characterizes the common freshwater turtle found in China, effectively naming the creature by its most notable visual trait.