You can edit any locale's phrases. You can use this to make small changes to a locale or completely update a cloned locale into a new language.
Locales are identified by ISO standard language (and sometimes territory) codes.
Each locale has standard data defined in the CLDR.
An 'i_' tag is a standard way to create, identify, and work with a non-standard locale by prefixing the code with the letter 'i' followed by an underscore.
You can use this tool to configure data that is defined by the CLDR for standard tags.