the.com/figure eight knot

means A simple stopper knot shaped like the numeral 8, tied in the end of a rope to keep it from running through a block, pulley, or your hands.

from Named plainly for what it looks like — two interlocking loops that trace the figure '8' when the knot is dressed and tightened. It's an old, widely used knot in sailing and climbing; its name is purely descriptive rather than a story of invention, though sailors have relied on this shape for centuries because its bulk holds fast under load yet unties easily compared to an overhand knot, which tends to jam tight and bite into itself.