What is the origin of ferrule?

To the casual observer, ferrule “a ring or cap put around the end of something” looks like it is a compound of Latin ferrum “iron” (compare the chemical symbol Fe and Spanish hierro) and the suffix -ule “small, little,” but looks can be deceiving. In fact, ferrule is an alteration of English forms such as verrel or virl, with a spelling change based simply on an association with Latin ferrum. Verrel and virl derive from Latin viriola “small bracelet,” from viria “bracelet,” a word of Gaulish (continental Celtic) origin. As we learned from the recent Word of the Day cathartic, it is rather common to see folk etymology—spelling and pronunciation changes based on associations with unrelated words—at work in many languages. In English, folk etymology explains the spelling changes in words such as ferrule as well as author (by influence of authentic), gridiron (by influence of iron), and rosemary (by influence of rose and the name Mary). Ferrule was first recorded circa 1610.