Merriam-Webster Collegiate Dictionary - ferrule

 noun  Etymology: alteration of Middle English virole, from Anglo-French, from Latin viriola, diminutive of viria bracelet, of Celtic origin; akin to Old Irish fiar oblique  Date: 1611  1. a ring or cap usually of metal put around a slender shaft (as a cane or a tool handle) to strengthen it or prevent splitting  2. a usually metal sleeve used especially for joining or binding one part to another (as pipe sections or the bristles and handle of a brush)  • ~d adjective