AFAIK, only a single control per module can have a blank key - the default control, that gets its name from the tabmodule.

For all other controls, enter a key e.g. "Settings" and add "controlTitle_settings" (key name in lower caps!) to the resource file of the control.

Module title is entered by the page author - so translation is only needed for multilingual (ML) sites with content in multiple languages. you need 3rd party modules, to provide ML content as well as ML page and module properties.