打ち込む
うちこむ · uchikomu · JLPT N1 · verb-godan
to devote oneself to
🎯 打 (strike) + 込む (push into): strike and drive yourself in, so you devote fully.
打ち込む means to shoot into or to throw yourself into something. Think of hammering a nail in fully: 打 hits, 込む drives it deep in. Same force, applied to effort or a target.
打 — hand radical 扌 + nail 丁
打 combines the hand radical 扌 (action with the hand) with 丁 (originally a nail), suggesting striking or hitting with the hand. 丁 also serves as a phonetic hint in older readings. The meaning broadened from 'to strike' to a general verb for many hand-based actions, like 打电话 'make a phone call'.