脑筋
nǎojīn · HSK 7
brain
🧠 脑筋 = 脑 brain + 筋 muscle/sinew, your brain-muscle that does the thinking
脑 means brain and 筋 means muscle or tendon, so 脑筋 is literally the brain-muscle you flex to think. It covers your head, your mind, and the ideas that muscle produces.
筋 — bamboo 竹 + flesh 月(肉) + strength 力
A semantic compound: 月 (flesh) shows it relates to the body, 力 (strength) hints at muscular force, and 竹 (bamboo) suggests fibers like bamboo strands. Together they depict the sinews or tendons that give the body its strength.