打ち消し
うちけし · uchikeshi · JLPT N1 · noun
negation
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'.
消 — water 氵 + 肖 (phonetic)
消 is a semantic-phonetic compound: the water radical 氵 indicates the meaning, while 肖 (xiào) supplies the sound. It originally described water dwindling or melting away, and from there extended to the modern senses of vanishing, dissolving, and dispelling.