Ferrule
Ferrule turns up in 2 fields: fiber optics, woodworking. Here is what it means to the people in each one.
Ferrule in fiber optics
The precision ceramic or metal cylinder in a connector that holds the fiber and lines it up with its mate.
A cylinder, usually zirconia ceramic, with a center hole bored to about 125 µm to hold the stripped fiber in epoxy or by mechanical clamp. The end is polished together with the fiber to form the connector end face. Ferrules come in 2.5 mm diameter for SC, ST and FC connectors and 1.25 mm for LC, and they align inside the split sleeve of an adapter.
"There's epoxy bead on the ferrule tip, take it down on the 5 micron film before you even think about the fine paper."
Ferrule in woodworking
A metal ring or cap placed on the handle of a hand tool to prevent the wood from splitting.
This reinforcing band is fitted around the end of a wooden tool handle right where the metal shank or tang enters the wood. Chisels, gouges, and files rely on ferrules to absorb the outward pressure created when the tool is struck or pushed heavily. Without this metal collar, the wooden handle would quickly crack under the stress of normal use.
"The ferrule on my favorite bench chisel is loose, so the handle rattles when I strike it."