The Collaborative International Dictionary of English v.0.48:

Lombard \Lom"bard\, prop. n. [F. lombard, fr. the Longobardi or
   Langobardi, i. e., Longbeards, a people of Northern Germany,
   west of the Elbe, and afterward in Northern Italy. See
   Long, and Beard, and cf. Lumber.]
   1. A native or inhabitant of Lombardy.
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   2. A money lender or banker; -- so called because the
      business of banking was first carried on in London by
      Lombards.
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   3. Same as Lombard-house.
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            A Lombard unto this day signifying a bank for usury
            or pawns.                             --Fuller.
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   4. (Mil.) A form of cannon formerly in use. --Prescott.
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   Lombard Street, the principal street in London for banks
      and the offices of note brokers; hence, the money market
      and interest of London.
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WordNet (r) 3.0 (2006):

Lombard Street
    n 1: a street in central London containing many of the major
         London banks