Ok, so Adriel has, in the past, so many times checked the meaning and history of the word bitter end that I may as well write it out before dementia takes hold. The better term for a Trump hold out is dead ender but bitter ender applies as well. The bitter is not the bitter taste left in the mouth after hearing a MAGA bitter ender bemoan whatever loss his leader has sustained. The bitter that tastes like rich, dark coffee is probably related to the word bite (BTW: a sense of bitter taste is genetic I hear, some people can’t taste bitter). The bitter in bitter end probably is related to bit, as small piece. A bitter is a post on a ship or other sailing vessel or on a dock. A rope is tied and wrapped around the bitter and used to belay, that is, to tie something down like to fasten the ship to the dock. So if that rope plays out its length, the very last end will be at the bitter. The bitter end.
I am getting much of this from https://www.etymonline.com/ because I know zilch about seafaring. I do know I’ll hold out for Barack Obama’s brilliant legacy to the bitter end.
Two Strikes 