Ferrule

[fer-uh l, -ool] /ˈfɛr əl, -ul/

noun
1.
a ring or cap, usually of metal, put around the end of a post, cane, or the like, to prevent splitting.
2.
a short metal sleeve for strengthening a tool handle at the end holding the tool.
3.
a bushing or adapter holding the end of a tube and inserted into a hole in a plate in order to make a tight fit, used in boilers, condensers, etc.
4.
a short ring for reinforcing or decreasing the interior diameter of the end of a tube.
5.
a short plumbing fitting, covered at its outer end and caulked or otherwise fixed to a branch from a pipe so that it can be removed to give access to the interior of the pipe.
6.
Angling.

verb (used with object), ferruled, ferruling.
7.
to furnish with a ferrule.
/ˈfɛruːl; -rəl/
noun
1.
a metal ring, tube, or cap placed over the end of a stick, handle, or post for added strength or stability or to increase wear
2.
a side opening in a pipe that gives access for inspection or cleaning
3.
a bush, gland, small length of tube, etc, esp one used for making a joint
verb
4.
(transitive) to equip (a stick, etc) with a ferrule
n.

“metal cap on a rod,” 1610s, ferule, earlier verrel (early 15c.), from Old French virelle, from Latin viriola “bracelet,” diminutive of viriae “bracelets,” from a Gaulish word (cf. Old Irish fiar “bent, crooked”); spelling influenced by Latin ferrum “iron.”