He appeared diffident during the interview and hesitated to talk about his achievements.

diffident 是形容词，由前缀 dif-（表示"远离、缺乏"）和词根 fid（表示"信任、信心"）组成，字面意思是"缺乏信心的"。这个词描述一个人因为缺乏自信而显得害羞或犹豫不决的状态。