PLUGIN_ADMIN.HELP - where defined

The system default blueprint at /system/blueprints/pages/default.yaml contains lines like this:
help: PLUGIN_ADMIN.PUBLISHED_HELP
Can someone tell me where those constants are defined? (Apologies if this has already been answered - searched but didn't find.)

With the Admin plugin installed, in the .yaml files of the different languages in /user/plugins/admin/languages.

You did not find it because the file structure is:

PLUGIN_ADMIN:
   ...
   PUBLISHED_HELP
   ...
``