open-mouthed

The compound adjective 'open-mouthed' is a transparent formation from native English elements. Its first element, 'open', derives from the Old English 'open', meaning uncovered or accessible, a concept with deep Proto-Germanic roots. The second element, 'mouth', originates from Old English 'mūþ', referring to the oral cavity, itself from Proto-Germanic 'munþaz'. The literal combination, "having a mouth that is open," has been used since the 16th century to vividly depict a physical state of gaping. This literal image was then metaphorically extended to describe the psychological states that cause such a reaction—primarily astonishment or insatiable eagerness—demonstrating how a concrete physical descriptor evolves into an abstract character trait.

Structure: open (exposed) + mouth (oral cavity) + ed (adjective suffix) - open: From Old English 'open' (not closed, accessible), of Germanic origin, related to Old Norse 'opinn'. Functions as an adjective/adverb modifying the state of the following noun. - mouth: From Old English 'mūþ' (opening through which food is taken), of Germanic origin. Functions as the core noun specifying the body part. - ed: A suffix forming adjectives from nouns or other adjectives, indicating possession of a quality. From Old English '-ede', '-ode', '-ad'.