The word 'stinking' is a straightforward combination of the ancient verb 'stink' and the adjectival suffix '-ing'. The root 'stink' originates from the Proto-Germanic stinkwaną, which carried the sense of to smell or emit an odor, a meaning it broadly retained in Old English. Over time, its usage narrowed almost exclusively to denote foul or offensive smells. The addition of the '-ing' suffix, a common Germanic participial ending, transforms the action of smelling badly into a descriptive state, literally meaning "engaged in the act of stinking." This literal sense of foul odor naturally evolved into a powerful intensifier in informal English, used to express extreme displeasure or to amplify negative qualities, following a common linguistic pattern where strong sensory words gain metaphorical force.

Structure: stink (to smell very bad) + ing (adjective-forming suffix) - stink: From Old English stincan, meaning "to emit a smell," often a bad one. Its functional role is the core semantic root. - ing: A suffix of Old English origin, used to form present participles and adjectives from verbs. Its functional role is to convert the verb into an adjective describing a state or quality.