Yes, it's true! I'm the author of ping for UNIX. Ping is a little thousand-line hack that I wrote in an evening which practically everyone seems to know about. :-) I named it after the sound that a sonar makes, inspired by the whole principle of echo-location. In college I'd done a lot of modeling of sonar and radar systems, so the "Cyberspace" analogy seemed very apt. It's exactly the same paradigm applied to a new problem domain: ping uses timed IP/ICMP ECHO_REQUEST and ECHO_REPLY packets to probe the "distance" to the target machine.