Why does whitman use the word "untranslatable" to describe the speaker? what does "barbaric yawp" suggest about the speaker's message to the world?

He uses the term to describe how the person who is speaking is much like a hawk: free and almost in a state of nature. He also uses this term to show how the person is not able to be understood when they are speaking. The speaking is almost wild and, as such, is reminiscent of the call of a hawk.