The "ping" command is built into both Windows and UNIX machines as a universal way of testing network response time and performance. The name is really based off the similarity to sonar pings, though many people have create a post hoc acronym "Packet INternet Groper".
Example: The ping-of-death attack used IP fragmentation to crash systems. It was so named because the ping program built-in to Windows could be easily told to fragment packets this way.
Key point: Even though the ping program is simple, it can be abused. Some versions can be commanded to send packets as fast as possible, which is often done to flood networks. Most versions allow the packet size to be set to a large size, forcing fragmentation. When used with the flood above, it can overload machines since fragmentation reassembly is so slow.
Contrast: There is an IRC command called "PING" that is unrelated to the ICMP ping. It is simply the text string "PING", where the target replies with "PONG".
Birds are different in Mexico.