ferrule
/ˈferuːl/(亦作 ferrel)
noun
1- a ring or cap, typically a metal one, which strengthens the end of a handle, stick, or tube and prevents it from splitting or wearing（把手、手杖、管子顶端防裂或防磨损的）金属箍; 金属包头。
1.1
- a metal band strengthening or forming a joint（用于加固或构成接头的）金属套圈, 箍。
词源
early 17th cent.: alteration （probably by association with Latin ferrum 'iron'） of obsolete verrel, from Old French virelle, from Latin viriola, diminutive of viriae 'bracelets'.