1. A ring or cap placed around a pole or tool handle to strengthen it or prevent splitting.
2. In plumbing, a short tube or bushing used to secure a pipe joint.
ferule (fĕr′əl) noun.
An instrument, such as a rod, cane, or flat piece of wood, used to punish children.
Ferrule (early 1600s) comes from the old French virelle, which is from Latin viriola, "little bracelet".
Ferule (late 1500s) comes from the Middle English ferula, which is from Latin ferula, rod, reed, whip, or fennel plant.
Before it meant "rod used to punish children", ferule meant "giant fennel". Yep.
Giant fennel isn't a true fennel, being in the genus Ferula (along with asafoetida) rather than the genus Foeniculum (which contains the culinary fennel).