Why is The Constant Gardener called The Constant Gardener?

I think I read that one and I definitely saw the movie. I don't know what it means to be truthful. This is what I think. Ralph Fiennes' character is the Gardener. And he is a good man. He has not taken a lot of risks in his life, is not a hero, but is a decent person. He is steady and constant. When his wife is murdered he takes it upon himself to find out who did it. Again he is not much the heroic type but here also his constancy is shown. He won't give up the search for anything even if it should lead to his death. So in a sense he is a true hero: an ordinary person who risks everything for the truth and the woman he loved.