loudmouth

the compound "loudmouth" is a transparent modern english formation, combining two ancient germanic roots. the first element, "loud," descends from proto-germanic \hlūdaz, itself from the proto-indo-european root \ḱleu- meaning "to hear," giving the sense of something easily heard. the second element, "mouth," comes from proto-germanic \munþaz, of uncertain pie origin. the compound's logic is entirely literal, metaphorically characterizing a person whose speech is excessively audible and often indiscreet. this figurative use, shifting from a physical description to a label for a brash personality, emerged in american english in the early 20th century.

Structure: loud (adjective) + mouth (noun) loud (from old english hlūd, meaning "making a lot of noise, heard far and wide"; functions as an adjective modifier). mouth (from old english mūþ, meaning "oral opening, speech organ"; functions as the core noun).