the.com/watch chain

means A short decorative chain that anchors a pocket watch to a vest, belt loop, or jacket so the watch can be tucked away safely and pulled out with a flourish when needed.

from Rooted simply in 'watch' (from Old English wæcce/wæccan, 'to be awake,' since early watches were tools for keeping track of time while on watch or duty) plus 'chain' (from Old French chaeine, tracing to Latin catena, 'chain, fetter'). Pocket watches became common from the 1600s onward, and once they did, owners needed a way to keep an expensive, slippery object from sliding out of a pocket and shattering on the floor — the chain, often clipped to a waistcoat buttonhole, was the practical answer that also became a flash of personal style, dangling fobs and seals along its length.