People who talk a lot may not be good at doing things. A man who is interested in doing things and is capable of doing things is not likely to waste much time talking about them. He is busy that he has no time to talk. The man who cannot do much work spends his time taking about that he can do.
He imagines he can do a lot of work and talks about his imaginary talents. Cowards often boast of the heroic deeds they have done. Everyone knows that those heroic deeds never took place. Barking dogs rarely bite. Barking symbolizes taking, and biting symbolizes activity.