The difference between Informant and Name names

Informant as a noun:

One who relays confidential information to someone, especially to the police; an informer.

Informant as a noun (linguistics):

A native speaker who acts as a linguistic reference for a language being studied. The informant demonstrates native pronunciation, provides grammaticality judgments regarding linguistic well-formedness, and may also explain cultural references and other important contextual information.

Name names as a verb (idiomatic):

To identify specific people, especially people involved in misdeeds or other secretive activity.