The compound adjective 'well-built' is a transparent combination of two Germanic elements. The adverb 'well,' with its Proto-Germanic root wel, conveys the concept of goodness or satisfactoriness. It modifies the past participle 'built,' derived from the Old English verb byldan, which is related to the concept of a dwelling (bold) and thus inherently linked to construction. The term's logic is straightforward: something that is "built well." This literal sense of solid construction was first applied to structures and objects. By the early 19th century, the metaphor was extended to the human body, describing a physique that appears strong and solidly constructed, leading to its common modern usage referring to a muscular and attractive bodily form.

Structure: well (in a good manner) + built (constructed) - well: From Old English wel, meaning "in a good manner, satisfactorily." It functions as an adverb modifying the participle. - built: Past participle of the verb build, from Old English byldan, meaning "to construct." It functions as the core descriptive element.