The line where one thing stops and another begins. Not a wall — a statement about where authority ends.
Anglo-French bunde, from Medieval Latin bodina/bodena, likely of Gaulish (Celtic) origin though the deeper root is not securely settled; a boundary was first a physical marker driven into the ground before it named the abstract limit.
The line where one thing's authority stops and another's begins — a statement about reach, not a wall built to keep anyone out.