口吟む
くちずさむ · kuchizusamu · JLPT N1 · noun
to humble
👄 口 (mouth) + 遊む (play) = the mouth plays a tune softly, so humming
Correction: 口遊む means to hum or murmur a tune under your breath, not to humble. To humble is 謙る (へりくだる). 口吟む is an alternate spelling.
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.