Sorry, Firefox doesn't have a user preference for that type of feature, although some extensions do use a "on-hover" of the cursor with some sort of display of the extension name - - but that is on Windows OS, which is what I use. The option for that was removed from Firefox on Windows OS's quite awhile ago.

Don't know if that is used for Mac OSX builds of Firefox, though.

Maybe a fellow Mac user will have a better answer for you ...

What items is this about ?

Is this about icons on the Navigation Toolbar or about bookmarks or otherwise ?

When I mention "items" above, I meant the icons that show up to the right of the search bar.

Hello,

Due to small size, It's not practically possible but however you can see name of your icons by hovering cursor on it.