The Collaborative International Dictionary of English v.0.48:

Quaker \Quak"er\, n.
   1. One who quakes.
      [1913 Webster]

   2. One of a religious sect founded by George Fox, of
      Leicestershire, England, about 1650, -- the members of
      which call themselves Friends. They were called Quakers,
      originally, in derision. See Friend, n., 4.
      [1913 Webster]

            Fox's teaching was primarily a preaching of
            repentance . . . The trembling among the listening
            crowd caused or confirmed the name of Quakers given
            to the body; men and women sometimes fell down and
            lay struggling as if for life.        --Encyc. Brit.
      [1913 Webster]

   3. (Zool.)
      (a) The nankeen bird.
      (b) The sooty albatross.
      (c) Any grasshopper or locust of the genus Edipoda; --
          so called from the quaking noise made during flight.
          [1913 Webster]

   Quaker buttons. (Bot.) See Nux vomica.

   Quaker gun, a dummy cannon made of wood or other material;
      -- so called because the sect of Friends, or Quakers, hold
      to the doctrine, of nonresistance.

   Quaker ladies (Bot.), a low American biennial plant
      (Houstonia c[ae]rulea), with pretty four-lobed corollas
      which are pale blue with a yellowish center; -- also
      called bluets, and little innocents.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nankeen \Nan*keen"\, n. [So called from its being originally
   manufactured at Nankin (Nanjing), in China.] [Written also
   nankin.]
   1. A species of cloth, of a firm texture, originally brought
      from China, made of a species of cotton (Gossypium
      religiosum) that is naturally of a brownish yellow color
      quite indestructible and permanent.
      [1913 Webster]

   2. An imitation of this cloth by artificial coloring.
      [1913 Webster]

   3. pl. Trousers made of nankeen. --Ld. Lytton.
      [1913 Webster]

   Nankeen bird (Zool.), the Australian night heron
      (Nycticorax Caledonicus); -- called also quaker.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Quaker
    n 1: a member of the Religious Society of Friends founded by
         George Fox (the Friends have never called themselves
         Quakers) [syn: Friend, Quaker]
    2: one who quakes and trembles with (or as with) fear [syn:
       quaker, trembler]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

QUAKERS. A sect of Christians.
     2. Formerly they were much persecuted on account of their peaceable
principles which forbade them to bear arms, and they were denied many rights
because they refused to make corporal oath. They are relieved in a great
degree from the consequent penalties for refusing to bear arms; and their
affirmations are everywhere in the United States, as is believed, taken
instead of their oaths.