An eponym is the name of a person, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named. One who is referred to as eponymous is someone that gives their name to something, e.g. Julian, the eponymous owner of the famous restaurant Julian's Castle. Something eponymous is named after a particular person, e.g. Julian's eponymous restaurant. In contemporary English, the term eponymous is often used to mean self-titled. An Etiological Myth is a "reverse eponym" in the sense that a legendary character is invented in order to explain a term.

Political eponyms of time periods

In different cultures, time periods have often been named after the person who ruled during that period.

• One of the first recorded cases of eponymy occurred in the second millennium BC, when the Assyrians named each year after a high official (limmu).

• In ancient Greece, the eponymous archon was the highest magistrate in Athens. Archons of Athens served a term of one year which took the name of that particular archon (e.g., 594 BC was named for Solon).

• In Ancient Rome, one of the two formal ways of indicating a year was to cite the two annual consuls who served in that year. For example, the year we know as 59 BCE would have been described as "the consulship of Marcus Calpurnius Bibulus and Gaius Julius Caesar" (although that specific year was known jocularly as "the consulship of Julius and Caesar" because of the insignificance of Caesar's counterpart). Under the empire, the consuls would change as often as every two months, but only the two consuls at the beginning of the year would lend their names to that year.

• Well into the Christian era, many royal households used eponymous dating by regnal years. The Roman Catholic Church, however, eventually used the Anno Domini dating scheme based on the birth of Christ on both the general public and royalty. The regnal year standard is still used with respect to statutes and law reports published in some parts of the United Kingdom and in some Commonwealth countries (England abandoned this practice in 1963): a statute signed into law in Canada between February 6, 1994 and February 5, 1995 would be dated 43 Elizabeth II, for instance.

• Government administrations or political trends often become eponymous with a government leader. North American examples include the Nixon Era, Trudeaumania, Jeffersonian economics, Jacksonian democracy, McCarthyism, Thatcherism, Kennedy's Camelot, or Reaganomics.

• British monarchs have become eponymous throughout the English speaking world for time periods, fashions, etc. Elizabethan, Edwardian, Georgian, and Victorian, are examples of these.