the adverb "stoutly" is built upon the adjective "stout," which entered english from old french "estout," meaning bold or proud. this old french term itself has germanic roots, likely connected to a proto-germanic word related to pride or swelling, which can metaphorically extend to notions of strength and boldness. the addition of the old english adverbial suffix "-ly" transforms the descriptive quality into a manner of action. thus, the literal sense of "in a strong or bold manner" evolved to describe both physical solidity and, more commonly, resolute and courageous behavior.

Structure: stout (strong, brave) + ly (adverb suffix) 'stout' is from middle english, from old french 'estout' (bold, proud), of germanic origin. 'ly' is an old english adverbial suffix.