How do people's names become regular words?

An eponym is a word derived from a person's name. Some commemorate inventors and namesakes: the saxophone from Adolphe Sax, diesel from Rudolf Diesel, pasteurization from Louis Pasteur, and the sandwich from the Earl of Sandwich, who reportedly wanted food he could eat without leaving his work or his card table. Others are less flattering to their sources. Boycott comes from Charles Boycott, a land agent in Ireland ostracized by an organized community campaign in 1880, meaning the word records a punishment rather than an achievement. Silhouette derives from French finance minister Etienne de Silhouette, whose austerity measures made his name a byword for things done cheaply.

Two adjacent categories are worth distinguishing. Some eponyms honor people who did not want the association, notably nicotine from Jean Nicot, who introduced tobacco to the French court, and the Ponzi scheme from Charles Ponzi, who did not invent the fraud but ran the version that made the papers. And many eponyms come from fiction or mythology rather than real people, including quixotic, scrooge, narcissism, and herculean. The process continues: to google became a verb quickly enough that the company's lawyers fought it, because a trademark that becomes a generic word can lose protection, which is what happened to aspirin, escalator, and zipper.