The Free On-line Dictionary of Computing (30 December 2018):

Direct Client to Client Protocol

    (DCC) An IRC protocol created to allow users
   to chat privately and to send and receive files directly
   instead of having to go thorugh the IRC servers.  DCC protects
   users from being monitored by IRC Server operators that have
   enabled conversation logging.  It also allows much more
   efficient use of available bandwidth as the data does not
   need to be broadcast all over the world just to reach a
   specific user.

   The available DCC commands include DCC CHAT (direct user to
   user chat), DCC SEND (direct user to user file send) and DCC
   GET (file acknowledgement from a receiver).

   (1995-04-12)