In the book, the word "Man" is mostly used by Lady Macbeth and Macbeth himself, but comparing to the real world. the book's "Man" shows more of a violence, showing that real "Man" should not be coward. But here in the word Coward, was not being cowardly to regular things, instead, Macbeth was coward towards to his feelings of killing Duncan, which I think as a man should have that type of hesitation. In real life, people just think that man should do anything without hesitation, and whenever you hesitate, they calls you coward and "Unman'.