Did you know that lots of common words come from proper nouns? Words based on people's names are a form of eponym (words derived from the name of a person or place). Some of these eponyms retain their capitalization but the words which have most clearly shifted to eponymous are those which are no longer capitalized. The words no longer refer to a specific person but to a general description of a thing or process. Usually the person, whose name serves as the basis for a word, was formative or gained notoriety related to a thing or process described by the word (think boycott, guillotine, and sandwich).
Many eponyms have interesting histories. There are words for units of measure derived from the scientists who contributed to the development of those units (baud, bel, Celsius, coulomb, curie, decibel, erlang, Fahrenheit, farad, faraday, fermi, fresnel, gal, gauss, gilbert, gray, hartree, henry - well, you get the idea). Scientists have also figured largely in the naming of things as they discover and classify what they have discovered (forsythia, freesia, fuchsia, lobelia, loganberry, magnolia, molly and guppy (types of aquarium fish), peony, poinsettia, rafflesia, sequoia, wisteria, zinnia, and so on). Some scientists are permanently associated with the diseases they identified (salmonella (actually it was discovered by Daniel Salmon's colleague, Theobald Smith, but Dan took the credit) and rickettsia).
Another group of people who have contributed greatly to our lexicon is cooks. People who invent delicious food have their names memorialized (béchamel, benedictine, chateaubriand, grog, madeleine, praline, pavlova, the previously mentioned sandwich, savarin, soubise, stroganoff, and many more).
Greek and Roman gods figure prominently in eponyms where examples include atlas, bacchanalia, cereal, dionysian, erotic, fauna, herculean, hermaphrodite, iris, January, jovial, June; just to name a few.
Characters in plays and books have also lent their names to general words, usually by describing a dominant characteristic of the character. A malapropism (a humorously misused or mispronounced word) originated with Mrs. Malaprop in The Rivals, a play by Richard Brinsley Sheridan (1751-1816). The large, baggy umbrella referred to as a gamp came from the character of Mrs. Sarah Gamp, in Charles Dicken's Martin Chuzzlewit. And the word hooligan got its start in a popular 1890's music-hall song about a rowdy Irish family by the name of Hooligan.
Some of the most interesting eponyms are those which describe an action or characteristic. Bowdlerize, meaning to heavily rewrite a document, comes to us from Thomas Bowdler (1734-1825) who published a sanitized version of Shakespeare so it could be read aloud to the family while preserving propriety. Burke, meaning to strangle or suffocate someone, started with William Burke who was executed in Edinburgh, Scotland for suffocating 16 people in order to sell their bodies to the Edinburgh Medical School. Chauvinism, meaning passionate, single-minded devotion to a cause, comes to us courtesy of Nicholas Chauvin, a French soldier famous for his devotion to Napoleon. Dunce, meaning a nincompoop or stupid person, began when John Duns Scotus (circa 1265-1308) a Scottish theologian, earned the ridicule of his readers for his writings and philosophy. Gerrymander, meaning to delineate electoral districts to include as many voters of a particular party as possible, was named after Massachusetts governor, Elbridge Gerry (1744-1814), who did just such a trick to give his party an advantage. Jackanapes, meaning a mischievous or impudent person, started with Jack Napis, the nickname of William de la Pole, Fourth Earl and First Duke of Suffolk (1396-1450). You can guess what he must have been like!
Eponyms are fascinating because they have such riveting stories behind them. You can find more by searching on the term "eponym" or phrases like "words based on people's names".