The Collaborative International Dictionary of English v.0.48:

Compounder \Com*pound"er\, n.
   1. One who, or that which, compounds or mixes; as, a
      compounder of medicines.
      [1913 Webster]

   2. One who attempts to bring persons or parties to terms of
      agreement, or to accomplish ends by compromises.
      "Compounders in politics." --Burke.
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   3. One who compounds a debt, obligation, or crime.
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            Religious houses made compounders
            For the horrid actions of their founders.
                                                  --Hudibras.
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   4. One at a university who pays extraordinary fees for the
      degree he is to take. [Eng.] --A. Wood.
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   5. (Eng. Hist.) A Jacobite who favored the restoration of
      James II, on condition of a general amnesty and of
      guarantees for the security of the civil and
      ecclesiastical constitution of the realm.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

COMPOUNDER, in Louisiana. He who makes a composition. An amicable compounder
is one who has undertaken by the agreement of the parties to compound or
settle differences. between them. Code of Pract. of Lo. art. 444.