含蓄
hán xù · HSK 7
reserved
含 hold-in-mouth + 蓄 store up = you keep words held back, not blurted = reserved
含 means to hold or contain (originally in the mouth) and 蓄 means to store or accumulate. Together: holding things in and storing them rather than letting them out, which is exactly what a reserved, restrained person or style does.
含 — mouth 口 + 今 (jīn, phonetic)
含 is a phono-semantic compound. The 口 (mouth) component gives the meaning — holding something in the mouth — while 今 supplies the sound. From the literal sense of keeping something inside the mouth, it extended to mean 'contain', 'include', or 'hold within'.