the adjective "whiny" is a modern english formation built upon the much older verb "whine." the verb itself originates from old english hwīnan, an onomatopoeic term imitative of a prolonged, high-pitched sound, such as a whizzing arrow or a humming insect. over time, this sense was figuratively extended to describe the sound of a plaintive human complaint or cry. by adding the productive adjectival suffix "-y," which denotes "characterized by," english created "whiny" to describe a person or tone habitually characterized by such fretful complaining, thus capturing a behavioral trait through its auditory signature.

Structure: whin(e) (to complain) + y (adjective suffix) whine (from old english hwīnan, meaning to make a whizzing or humming sound, of imitative origin) + y (from old english -ig, a suffix forming adjectives meaning "characterized by, full of, having the qualities of").