When it comes to secretive terminology, "code name" is a phrase that might immediately come to mind. However, there are several other phrases that can be used to describe a hidden or classified name. These include "alias," "moniker," "handle," "pseudonym," "nom de plume," and "nom de guerre." Depending on the context, "cover name," "false name," or "disguised name" could also be used. Ultimately, all of these phrases refer to a hidden or alternative name used for privacy or security purposes.