The Collaborative International Dictionary of English v.0.48:

Scaup \Scaup\ (sk[add]p), n. [See Scalp a bed of oysters or
   mussels.]
   1. A bed or stratum of shellfish; scalp. [Scot.]
      [1913 Webster]

   2. (Zool.) A scaup duck. See below.
      [1913 Webster]

   Scaup duck (Zool.), any one of several species of northern
      ducks of the genus Aythya, or Fuligula. The adult
      males are, in large part, black. The three North American
      species are: the greater scaup duck (Aythya marila, var.
      nearctica), called also broadbill, bluebill,
      blackhead, flock duck, flocking fowl, and raft
      duck; the lesser scaup duck (Aythya affinis), called
      also little bluebill, river broadbill, and shuffler;
      the tufted, or ring-necked, scaup duck (Aythya
      collaris), called also black jack, ringneck,
      ringbill, ringbill shuffler, etc. See Illust. of
      Ring-necked duck, under Ring-necked. The common
      European scaup, or mussel, duck (Aythya marila), closely
      resembles the American variety.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jack \Jack\, n. [Named from its resemblance to a jack boot.]
   A pitcher or can of waxed leather; -- called also black
   jack. [Obs.] --Dryden.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ring-necked \Ring"-necked`\, a. (Zool.)
   Having a well defined ring of color around the neck.
   [1913 Webster]

   Ring-necked duck (Zool.), an American scaup duck (Aythya
      collaris). The head, neck, and breast of the adult male
      are black, and a narrow, but conspicuous, red ring
      encircles the neck. This ring is absent in the female.
      Called also ring-neck, ring-necked blackhead,
      ringbill, tufted duck, and black jack.
      [1913 Webster]

U.S. Gazetteer Places (2000):

Black Jack, MO -- U.S. city in Missouri
   Population (2000):    6792
   Housing Units (2000): 2587
   Land area (2000):     2.660066 sq. miles (6.889540 sq. km)
   Water area (2000):    0.007305 sq. miles (0.018921 sq. km)
   Total area (2000):    2.667371 sq. miles (6.908461 sq. km)
   FIPS code:            06004
   Located within:       Missouri (MO), FIPS 29
   Location:             38.790799 N, 90.261885 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Black Jack, MO
    Black Jack