The Collaborative International Dictionary of English v.0.48:

Vichy water \Vi"chy wa`ter\, prop. n.
   A mineral water found at Vichy, France. It is essentially an
   effervescent aqueous solution of sodium, calcium, and
   magnesium carbonates, with sodium and potassium chlorides;
   also, by extension, any artificial or natural water
   resembling in composition the Vichy water proper. Called
   also, colloquially, Vichy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Vichy
    n 1: a town in central France (south of Paris) noted for hot
         mineral springs; was capital of the unoccupied part of
         France during World War II