綿裡藏針

lit. a needle concealed in silk floss (idiom) / fig. ruthless character behind a gentle appearance / a wolf in sheep's clothing / an iron fist in a velvet glove

Tibet / abbr. for Xizang or Tibet Autonomous Region 西藏[Xi1 zang4]

to conceal / to hide away / to harbor / to store / to collect

storehouse / depository / Buddhist or Taoist scripture

needle / pin / injection / stitch / CL:根[gen1],支[zhi1]

silk floss / continuous / soft / weak / mild-mannered (dialect)

lining / interior / inside / internal / also written 裏|里[li3]