The compound adjective "stick-thin" is a vivid example of a metaphorical comparison in English, formed by directly combining two native Germanic words. The noun "stick," with its ancient Proto-Germanic root stikkô meaning a pointed object or peg, is used to evoke the image of a long, narrow, and rigid piece of wood. When paired with the adjective "thin," derived from the Proto-Germanic thunnuz, the compound creates a powerful simile meaning "as thin as a stick." This construction follows a common English pattern for intensifying descriptions, where a concrete noun is hyphenated with an adjective to form a new, more expressive term. The logic is purely visual and metaphorical, drawing on the shared human experience of observing the slender shape of a twig to describe an extreme degree of leanness in a person's physique.

Structure: stick (noun) + thin (adjective) - stick: From Old English sticca, meaning a rod, twig, or slender piece of wood. In this compound, it functions as a noun used attributively to denote resemblance. - thin: From Old English þynne, meaning not thick, slender, or sparse. It functions as the core adjective describing the state of being slender.