reticence       
noun [ U ]  formal uk/ˈret.ɪ.səns/ us/ˈret̬.ə.səns/
 沉默寡言;不愿交谈
an unwillingness to do something or talk about something, for example because you are nervous or being careful
  His reticence about his past made them very suspicious. 他对自己的过去讳莫如深,使他们非常怀疑。 
 I think my dad had a certain reticence about showing love as he was afraid that people would leave if he did. 我觉得父亲不愿意表达爱意,因为他害怕如果他表达了,人们会离开他。 
 See: reticent
 - More examples
 - She had overcome her usual reticence and talked about their married life.
 - His reticence is understandable.
 - Despite his initial reticence, he began teaching the children.