the.com/zip line

means A taut cable strung between two points at different heights, letting a rider clipped to a pulley slide down by gravity alone.

from "Zip" imitates the brisk, whizzing sound of fast movement through air, a sound-word in English since the 1800s; "line" is simply the rope or cable itself. The compound is a 20th-century practical coinage — first used for utilitarian cable-and-pulley rigs to haul gear across rivers or down mountainsides, long before it became a tethered thrill ride. No ancient roots here, just a word built to sound exactly like what it does.