Translating entries in the Components menu
From Joomla! Documentation
Entries in the Components menu and its sub-menus may be translated using a mechanism that allows translators to include translations for third-party developer extension entries.
A language INI file in the administrator/language/<lang> directory, called <lang>.<component>.sys.ini will be loaded when the administrator menus are built and should contain language replacement strings for the menu item and its sub-menus.
For example, the Banners component, com_banners, has a menu translation string in administrator/language/en-GB called en-GB.com_banners.sys.ini which you will find among other strings:
COM_BANNERS="Banners" COM_BANNERS_CATEGORIES="Categories" COM_BANNERS_CLIENTS="Clients" COM_BANNERS_TRACKS="Tracks"
The first of these strings replaces the menu and sub-menu items for Banners in the Components menu. The other three replace sub-menu items within the Banner entry in the Components menu.