The Collaborative International Dictionary of English v.0.48:

Unconcerned \Un`con*cerned"\, a.
   Not concerned; not anxious or solicitous; easy in mind;
   carelessly secure; indifferent; as, to be unconcerned at what
   has happened; to be unconcerned about the future. --
   Un`con*cern"ed*ly, adv. -- Un`con*cern"ed*ness, n.
   [1913 Webster]

         Happy mortals, unconcerned for more.     --Dryden.
   [1913 Webster]