苦痛
くつう · kutsuu · JLPT N3 · noun
pain
🤕 苦痛 = bitter/suffering + pain: pain that tastes bitter
苦 (ku) means bitter or suffering, as in 苦い nigai, bitter. 痛 (tsuu) means pain, as in 痛い itai, it hurts. Put together, they make pain that is also suffering: agony. It is a formal word, often used in writing.
苦 — grass radical 艹 + 古 (old)
Originally referred to a bitter-tasting plant, with the grass radical 艹 indicating its botanical nature and 古 providing the phonetic element. The meaning extended from the literal bitter taste to figurative senses of hardship, suffering, and painful effort.
痛 — sickness radical 疒 + 甬 (yǒng, phonetic)
痛 is a semantic-phonetic compound. The 疒 radical depicts a person on a sickbed and signals illness or pain. The component 甬 supplies the sound, historically close to 'tòng'. Together they convey bodily ache, later extended to emotional pain and the adverbial sense 'thoroughly'.