conscience-money

Noun

conscience money (uncountable)

1. (idiomatic) Money which is voluntarily paid by a party who feels guilt, and seeks to provide compensation, for some past misdeed or negligence.
   • The Secretary of the Treasury is almost daily in receipt of installments of conscience-money, which the perturbed moral sense of a guilty office-holder or other defrauder of the government suggests the payment of in order to obtain "a still and quiet conscience."1865 November 23, “From Washington”, in New York Times, retrieved 24 Aug 2014