You could call it a wire cap. I had a college engineering project where we had to call things by specific names (Photovoltaics instead of solar panels) and if we called it anything else, we were docked points. I called the current leakage protector a "GFCI" and I was docked points because my prof. said it was called a "GFI." I thought this was bad, but this engineer has me beat!
