The Collaborative International Dictionary of English v.0.48:

Dauphin \Dau"phin\, n. [F. dauphin, prop., a dolphin, from L.
   delphinus. See Dolphin. The name was given, for some reason
   unexplained, to Guigo, count of Vienne, in the 12th century,
   and was borne by succeeding counts of Vienne. In 1349,
   Dauphiny was bequeathed to Philippe de Valois, king of
   France, on condition that the heir of the crown should always
   hold the title of Dauphin de Viennois.]
   The title of the eldest son of the king of France, and heir
   to the crown. Since the revolution of 1830, the title has
   been discontinued. Dauphiness

WordNet (r) 3.0 (2006):

dauphin
    n 1: formerly, the eldest son of the King of France and direct
         heir to the throne

U.S. Gazetteer Counties (2000):

Dauphin -- U.S. County in Pennsylvania
   Population (2000):    251798
   Housing Units (2000): 111133
   Land area (2000):     525.289370 sq. miles (1360.493165 sq. km)
   Water area (2000):    32.243331 sq. miles (83.509841 sq. km)
   Total area (2000):    557.532701 sq. miles (1444.003006 sq. km)
   Located within:       Pennsylvania (PA), FIPS 42
   Location:             40.324487 N, 76.804656 W
   Headwords:
    Dauphin
    Dauphin, PA
    Dauphin County
    Dauphin County, PA


U.S. Gazetteer Places (2000):

Dauphin, PA -- U.S. borough in Pennsylvania
   Population (2000):    773
   Housing Units (2000): 337
   Land area (2000):     0.442255 sq. miles (1.145436 sq. km)
   Water area (2000):    0.004607 sq. miles (0.011931 sq. km)
   Total area (2000):    0.446862 sq. miles (1.157367 sq. km)
   FIPS code:            18272
   Located within:       Pennsylvania (PA), FIPS 42
   Location:             40.366687 N, 76.931168 W
   ZIP Codes (1990):     17018
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Dauphin, PA
    Dauphin