I think that might be what it was called, I remember hearing it offhandedly in a Hades live stream a while back, in reference to a particular defensive dash. They said that having more of them, was better. I assume it's something to do with the amount of digital space your character takes up, and thus how likely/unlikely it is they are hit by an attack, as a result of moving around threats? I might be using the wrong term, but I could've sworn he said E-frames, but it was never explained when I've heard it. It was always used assuming everyone hearing the word already knew what it meant. I think I've also heard it used in the context of tournament fighter games, and the likelihood of being hit by an attack based on the actual character model vs hit box.