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

whois

   An Internet directory service for looking up names of people
   on a remote server.  Many servers respond to TCP queries on
   port 43, in a manner roughly analogous to the DDN NIC
   whois service described in RFC 954.  Other sites provide
   this directory service via the finger protocol or accept
   queries by electronic mail for directory information.  On
   Unix the client command is

   	whois -h server_name person_name

   You can also type "telnet server_name 43" and then type the
   person's name on a separate line.  For a list of whois
   servers, FTP/Gopher: sipb.mit.edu.  Or

   	whois -h sipb.mit.edu whois-servers

   As the above command demonstrates, whois can find information
   about things other than users, e.g. domains, networks and
   hosts.

   See also finger, X.500, white pages.