资料来源 : Webster's Revised Unabridged Dictionary (1913)

   {To knock off}, to cease, as from work; to desist.

   {To knock under}, to yield; to submit; to acknowledge one's
      self conquered; -- an expression probably borrowed from
      the practice of knocking under the table with the
      knuckles, when conquered. ``Colonel Esmond knocked under
      to his fate.'' --Thackeray.