The compound adjective 'thread-like' is a transparent formation from two native English elements. The first element, 'thread', originates from the Old English þrǣd, itself derived from the Proto-Germanic þrēduz, related to the verb 'to throw' in the sense of twisting fibers. The second element, '-like', stems from the Old English adjective līc ('body, form'), which evolved into a highly productive suffix for creating descriptive adjectives. The compound's logic is straightforwardly comparative: it directly describes an object's physical similarity to the long, slender, and flexible form of a thread, a concept that has remained consistent from its Germanic roots to modern scientific and descriptive usage.

Structure: thread (noun) + like (adjective-forming suffix) - thread: From Old English þrǣd, meaning a fine cord of fibrous material. Its functional role is the core noun denoting the object of resemblance. - like: From Old English līc, meaning having the form or appearance of. Its functional role is a suffix that forms adjectives meaning 'similar to' or 'characteristic of'.