the word 'stacked' is built upon the noun 'stack', which entered middle english from old norse 'stakkr', referring to a pile of hay or grain. the addition of the adjectival suffix '-ed', a common germanic participle ending, transforms it into a descriptor meaning 'formed into a stack'. the modern informal sense, describing a curvaceous physique, is a mid-20th century metaphorical extension, likening the pronounced contours of the body to a pile of distinct, layered objects. this evolution showcases a common pattern where a concrete term for physical arrangement acquires a figurative meaning in colloquial use.

Structure: stack (pile) + ed (adjective suffix) stack (from old norse 'stakkr', meaning haystack, pile); ed (from old english '-ed', '-od', '-ad', past participle and adjective-forming suffix)