Merriam-Webster’s Word of the Day is ferrule:
ferrule \FAIR-ul\ nounFerrule is a word with special significance for pencil users. A superior pencil with an eraser will almost always have a distinctive ferrule. In these images from The House on 92nd Street, for instance, the Dixon Ticonderoga ferrule is instantly recognizable. And even in a blurry videotape transfer of The Days and Nights of Molly Dodd, the Mongol ferrule is unmistakable. By their ferrules ye shall know them.
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)
“A band of metal called a ferrule is glued onto the end of the pencil where a recess has been cut, while at the same time a plunger presses an eraser plug into the ferrule. When the glue dries, everything is bliss.” — From an article by Steve Ritter in Chemical & Engineering News, December 16, 2002
“Making a brush is as simple as knotting and gluing bristles to the handle, and holding them in place by slipping a tight metal ferrule over the bond between bristle and handle.” — From a post at swatchgirl.com on May 15, 2013
Did you know?
“Ferrule” is a word for a simple metal band or cap of great versatility. The ferrule is ubiquitous. It is the cap at the end of a cane or crutch, a chair or table leg; it is the point or knob at the hub of an umbrella; it fits together tubes and pipes and binds paintbrush handles to bristles and pencils to erasers. In Middle English this universal thingamajig was called a “verrel.” That word commonly referred to the strengthening bands or rings of iron used to prevent the splitting or wear of the wooden shafts of implements. The name evolved from Middle French “virelle” and Old French “virol” and ultimately from Latin “viriola,” meaning “small bracelet.” The “f” spelling of today's “ferrule” was influenced by “ferrum,” the Latin word for “iron.”