The word 'twiggy' is a straightforward English formation, combining the noun 'twig' with the adjectival suffix '-y'. Its core logic is directly descriptive: something that is 'of or like a twig'. The primary modern sense, describing a person as thin and slender, is a metaphorical extension from the 20th century, vividly comparing the thinness of human limbs to delicate woody shoots. This usage was notably popularized in the 1960s by the model Lesley Lawson, known by the nickname "Twiggy," whose physique epitomized this slender aesthetic. Thus, the word evolved from a literal descriptor of objects abounding in twigs to a culturally potent metaphor for a specific body type.

Structure: twig (slender woody shoot) + y (adjective-forming suffix) - twig: From Old English twigge, a slender branch or shoot. Its origin is Proto-Germanic, related to the concept of something that forks or divides. - y: A native English suffix (from Old English -ig) used to form adjectives meaning "characterized by" or "full of."