退治
たいじ · taiji · JLPT N1 · noun
extinction
退 — walk radical 辶 + 艮 (stop/halt)
退 combines the walking/movement radical 辶 with 艮, which carries a sense of stopping or turning back. Together they depict the action of moving backward or withdrawing. The original sense of retreating or stepping back has remained stable through history.
治 — water radical 氵 + 台 (phonetic)
治 originally referred to the name of a river, written with the water radical 氵 for meaning and 台 as the phonetic component. From 'managing rivers' (flood control), the meaning broadened to 'govern, regulate, manage,' and later 'cure, heal' — all senses of bringing something unruly under control.