The word "王八" (wángba) is formed through a process of cultural association and metaphorical extension. It originally referred to a specific mythical creature, often depicted as a turtle with a distinctive shell pattern, where the character "王" (king) and "八" (eight) were thought to visually describe the pattern on the creature's back. Over time, this term was adopted as a vulgar slang for a "turtle" or "tortoise". From this animal reference, it evolved into a severe insult implying cowardice (like an animal that hides in its shell) and, most notably, became a derogatory term for a man whose wife is unfaithful, drawing a metaphorical link to the supposed behaviour of certain turtles. Thus, its formation is not grammatical but is rooted in visual folklore, animal symbolism, and societal metaphor.