He was asked to stop his tiresome habit of tapping his pen during the lecture.

tiresome 是由名词 tire（疲劳）加上后缀 -some 构成的形容词。-some 这个后缀表示"具有...特性的"或"容易引起...的"。 tiresome 字面意思是"容易引起疲劳的"，引申为"令人厌烦的、烦人的"，用来描述那些让人感到疲惫或不耐烦的行为或事物。