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

Secure Shell

    (ssh) A Unix shell program for logging
   into, and executing commands on, a remote computer.  ssh is
   intended to replace rlogin and rsh, and provide secure
   encrypted communications between two untrusted hosts over an
   insecure network.  X11 connections and arbitrary TCP/IP
   ports can also be forwarded over the secure channel.

   (http://cs.hut.fi/ssh/).

   (1997-01-07)