Ferrule

A ferrule is any of a number of types of objects generally used for fastening, joining, sealing or reinforcement. The word is a corruption of the Latin viriola, meaning small bracelet, shaped by the influence of ferrum, meaning iron. Ferrules are often narrow circular rings made from metal or, less commonly, plastic, and in the manufacturing industry they are also often called eyelets or grommets. Most ferrules are circular clamps that hold together and attach fibers, wires or posts, generally by crimping, swaging or otherwise deforming the ferrule so that it tightens permanently onto the parts it holds.