The Collaborative International Dictionary of English v.0.48:

Blain \Blain\ (bl[=a]n), n. [OE. blein, bleyn, AS. bl[=e]gen;
   akin to Dan. blegn, D. blein; perh. fr. the same root as E.
   bladder. See Bladder.]
   1. An inflammatory swelling or sore; a bulla, pustule, or
      blister.
      [1913 Webster]

            Blotches and blains must all his flesh emboss.
                                                  --Milton.
      [1913 Webster]

   2. (Far.) A bladder growing on the root of the tongue of a
      horse, against the windpipe, and stopping the breath.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blain
    n 1: an inflammatory swelling or sore

U.S. Gazetteer Places (2000):

Blain, PA -- U.S. borough in Pennsylvania
   Population (2000):    252
   Housing Units (2000): 102
   Land area (2000):     0.352879 sq. miles (0.913952 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.352879 sq. miles (0.913952 sq. km)
   FIPS code:            06824
   Located within:       Pennsylvania (PA), FIPS 42
   Location:             40.337233 N, 77.510525 W
   ZIP Codes (1990):     17006
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Blain, PA
    Blain