rowel

If you've seen Western movies, you've seen rowels. The noun rowel names the circular, point-covered disk on the end of a spur that is used to urge powerful steeds to maximum speeds. But cowboys didn't invent rowels; knights in shining armor were sporting them even before the 12th century. English speakers of yore picked up the noun rowel from the Anglo-French roele, meaning "small wheel" (roele is also an ancestor of the word roulette). By the end of the 1500s, rowel was also being used as a verb for any process of prodding or goading that was as irritating as being poked in the side with a rowel.