John S. Farmer, Slang and its analogues past and present…
“ Hackle, subs. (common) .—Pluck; spirit; bottom (q.v.) . To show hackle = to show fight. [Hackle = a long shining feather on a cock’s neck.] Fr., avoir du foie; n’avoir pas le flubart, or avoir du poil au ciel. Hackslaver, verb. (old) .—To stammer; to splutter; to hesitate in speech. Hackum (or Captain Hackum, or Hackster) , subs. (old) .—A bully; a bravo. For synonyms, see Furioso. 1657. Lady Alimony, 1, 3 (Dodsley, Old Plays, 4th ed., 1875, xiv., p. 282) . Vowing, like a desperate haxter that he has express command to seize upon all our properties. ”
