This had a strange term but I can't remember what it's called and it's difficult to search for.
At our studio (Ubisoft Toronto) we usually call it a (low) health vignette.
A vignette in photography & film refers to an effect around the edges of the frame (usually a darkening or defocus) like this:
By attaching modifiers to it like "low health" or "super" etc. we express "that effect at the edges of your screen when you're in the ______ state"
Here are some sources that also call it a health vignette:
If it's particularly intrusive into the middle of the frame, we call it "strawberry jam" ;)