無口
むくち · mukuchi · JLPT N1 · na-adj
reticence
🤐 無 = without, 口 = mouth: a mouth with nothing coming out, so 'mu-ku-chi' is the quiet mouth.
Read it as 'no mouth': the characters literally say 'without mouth', so someone who keeps their mouth closed shows reticence. Compare 無理 (impossible) to see 無 meaning 'without'.
口 — pictograph of an open mouth
口 is one of the oldest pictographs in Chinese, originally drawn as a simple outline of an open mouth. Its core meaning 'mouth' extended naturally to 'opening' or 'entrance', as in 入口 (entrance). It also serves as a common radical in characters related to speech, eating, or apertures.