It is often believed that "Ping" is an abbreviation for Packet Internet Groper, but Ping's author has stated that the names comes from the sound that a sonar makes.

Connected Encyclopedia's desciption of Ping
Explains in some detail what Ping is, what it can and can't do, and how to use it, with sample traces.

Examine your Network Speed with Ping
HotWired Webmonkey article (October 1997) on examining your network with Ping to see if network traffic or a site itself is to blame for a slowdown. Focuses on The "Time To Live" field of a Ping session.

The Story of the PING Program
A history of the PING Program, written by the author, Mike Muuss.