The Collaborative International Dictionary of English v.0.48:

Heartedness \Heart"ed*ness\, n.
   Earnestness; sincerity; heartiness. [R.] --Clarendon.
   [1913 Webster]

   Note: See also the Note under Hearted. The analysis of the
         compounds gives hard-hearted + -ness, rather than hard
         + heartedness, etc.
         [1913 Webster]