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

nslookup

    A Unix utility program, originally by Andrew
   Cherenson, for querying Internet domain name servers.  The
   basic use is to find the IP address corresponding to a
   given hostname (or vice versa).  By changing the query type
   (e.g. "set type=CNAME") other types of information can be
   obtained including CNAME - the canonical name for an alias;
   HINFO - the host CPU and operating system type; MINFO -
   mailbox or mail list information; MX - mail exchanger
   information; NS - the name server for the named zone; PTR -
   the hostname if the query is an IP address, otherwise
   the pointer to other information; SOA the domain's
   start-of-authority information; TXT - text information; UINFO
   - user information; WKS - supported well-known services.
   Other types (ANY, AXFR, MB, MD, MF, NULL) are described in
   RFC 1035.


(ftp://src.doc.ic.ac.uk/computing/operating-systems/unix/bsd-sources/usr.sbin/named/tools/nslookup/).

   (1994-10-27)