Is there a specific name for this kind of ui component? Sometimes it only renders a symbol (without text) so using name like
TextComponent is imo not very fitting.
Not formally, but I usually see them referred to as "damage floaters." In the occasions where they do not actually convey damage, they're usually called "some other kind of floater," or just "floaters."
Et cetera. You can find several other references via Google searches (I'd recommend you include the term "UI" in the search though; otherwise you tend to get a lot of results about retina detatchment and such, which are decidedly unrelated).