Nassau
A bet split into three separate matches in one round: the front 9, the back 9, and the full 18, each settled on its own.
It's named after Nassau Country Club on Long Island, where club captain John B. Coles Tappan is credited with inventing the format around 1900, splitting the bet into thirds specifically so a poor front nine wouldn't decide the whole match.
A common add-on is the "press," a new bet for the same stakes that either player can call once they're down by 2 holes, giving them a fresh match to try to win even after the original one looks lost.