原爆
げんばく · genbaku · JLPT N1 · noun
atom bomb
原 — cliff 厂 + spring 泉 (white 白 + water 水)
Originally a pictograph showing a spring of water flowing out from beneath a cliff, depicting the source of a stream. From this concrete image of a water source, the meaning extended to 'origin,' 'source,' and 'original.' A separate character 源 was later created with the water radical 氵 to keep the literal 'spring' sense.
爆 — fire 火 + 暴 (violent/sudden, phonetic)
A semantic-phonetic compound: 火 (fire) gives the meaning, while 暴 (sudden, violent) supplies the sound and reinforces the sense. Originally meant to burst or explode with fire, later extended to any sudden, forceful eruption like popping or bursting.