The Collaborative International Dictionary of English v.0.48:

Rochelle \Ro*chelle"\, n.
   A seaport town in France.
   [1913 Webster]

   Rochelle powders. Same as Seidlitz powders.

   Rochelle salt (Chem.), the double tartrate of sodium and
      potassium, a white crystalline substance. It has a
      cooling, saline, slightly bitter taste and is employed as
      a mild purgative. It was discovered by Seignette, an
      apothecary of Rochelle, and is called also Seignete's
      salt.
      [1913 Webster]