/
I named the Creeper "LOL", and when I killed it, it said: "You just Killed a: LOL".
The same entity id display works with bow kills.
In this screenshot, I killed a husk with a splash potion of healing, and the kill message appeared!
I killed a creeper by hitting an end crystal and got the display name of the creeper!
I killed a creeper, and it says: "You Just Killed a: Creeper"

This mod tells you what you killed in the action bar! Useful to know what mob you killed!