Left horse radical (Kangxi #187) - the compressed left-side form of
马, simplified from
馬 in the 1956 reform. Carries the core meaning: the original sense of
驱 is 'to drive horses forward,' from which came the modern 'to expel, urge on, propel.' Same radical anchors
骑 (ride),
驰 (gallop),
驾 (harness),
骏 (fine steed) - all the equestrian-action verbs.