The Collaborative International Dictionary of English v.0.48:

Casehardened \Case"hard`ened\, a.
   1. Having the surface hardened, as iron tools.
      [1913 Webster]

   2. Hardened against, or insusceptible to, good influences;
      rendered callous by persistence in wrongdoing or
      resistance of good influences; -- said of persons.
      [1913 Webster]