The compound adjective 'well-padded' is a straightforward combination of two English elements. The adverb 'well,' with its Old English origins in words denoting goodness and abundance, is used here as an intensifier meaning "thoroughly" or "amply." It modifies the adjective 'padded,' which derives from the 16th-century verb 'pad,' likely of imitative origin related to the soft sound of footsteps or the action of stuffing. The literal, physical sense of "amply stuffed with soft material" (as in furniture or protective gear) naturally extended to a more figurative, often euphemistic, description of a person's plump or fleshy physique, emphasizing a sense of soft fullness rather than bony leanness.

Structure: well (thoroughly) + padded (filled with soft material) - well: From Old English wel, meaning "in a good way, thoroughly, abundantly." It functions as an intensifying adverb in compound adjectives. - padded: From the verb pad, meaning "to fill or cover with soft material." The suffix -ed forms the past participle, which functions as an adjective meaning "having been filled/covered."