You can reset all your changes to the names of individual instruments and revert them to the current default settings for their instrument type.
Resetting instrument names does not change the name shown at the top of part layouts. If you want to change the name used at the top of part layouts, rename the layout.
Procedure
Result
The instrument names for the selected instrument are reset to the current default settings for its instrument type. If you changed the default name for the instrument type or the instrument name language setting after adding the instrument, resetting its names changes them to your new default names and language setting.
You can assign a key command for Reset Instrument Names on the Key Commands page in Preferences, which resets all instrument names in the project to their default settings.