The Collaborative International Dictionary of English v.0.48:

Haw \Haw\, v. i.
   To stop, in speaking, with a sound like haw; to speak with
   interruption and hesitation.
   [1913 Webster]

         Cut it short; don't prose -- don't hum and haw.
                                                  --Chesterfield.
   [1913 Webster]

   hemming and hawing speaking hesitantly and inarticulately,
      with numerous pauses and interjections.
      [PJC]