Ferrule

ferrule \ˈfer-əl, ˈfe-rəl\ noun: 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)

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

Ferrule is one of those words that’s either mundane or exotic, depending on one’s background. Artists, for example, know not to let ferrules stay wet after washing their brushes, lest it lead to rust and bristle rot.