Secure Shell allows you to make encrypted connections to and from other hosts on the internet.
To verify that you really are connecting to the host you think you are, ssh keeps a "fingerprint" for each host you connect to. Unfortunately, it bases this fingerprint on the hostname you use, rather than the actual hostname of the remote system.
This means that if a remote system is known by multiple names, and you connect using different names, ssh will save a separate fingerprint for each name you use.
It also means that if a name points to more than one system (hpux.dc.engr.scu.edu is a good example), you are very likely to see warnings that the fingerprint does not match.