結核
けっかく · kekkaku · JLPT N1 · noun
tuberculosis
🫁 結 (knot) + 核 (core): TB forms hard nodules, so the word means knot-core
結核 was coined to translate German Tuberkel, meaning small nodule, the lesion TB forms. 結 means tie or knot; 核 means kernel or core.
核 — wood 木 + 亥 (phonetic)
A semantic-phonetic compound: 木 ('wood/tree') gives the meaning, while 亥 supplies the sound. It originally referred to a hard-shelled fruit pit or kernel inside wood/fruit, then extended figuratively to 'core,' 'nucleus,' and in modern usage 'nuclear' (as in atomic nucleus).