The word "猪头" is formed through a straightforward visual and conceptual analogy. It directly combines the character for "pig" (猪) with the character for "head" (头) to create a single, concrete image, literally a pig's head. This composite image is then applied metaphorically to a person, comparing their head (and by extension, their mind or behavior) to that of a pig, which in Chinese culture is stereotypically associated with foolishness, clumsiness, or gluttony. Thus, the term is built by painting a vivid, unflattering picture to convey an insult.