Left horse radical - the indexing radical. Pictograph of a horse with mane and legs (simplified from
馬). Originally
驳 named a piebald, mottle-coated horse; the 'mixed colors' meaning generalized to 'mixed-up arguments,' then specialized into 'refute, contradict' - countering opposing claims. Family:
骑 ride,
骄 proud,
骏 fine horse.