@Wordman : while we’re on the subject of Greco-Roman myth and fame :
Platonic love, i.e. pure, sexless love) Jovial, meaning cheerful. From the Latin declension of Jupiter’s name. When you’re being jovial, you belong to Jupiter.
The guillotine, named after its first proponent (but not inventor), Dr. Guillotin. He believed a painless, mechanical means of “more humane” execution would be the first step towards abolishing the death penalty alltogether. Boy was he in for disappointment…
The sandwich, named after the 4th Earl of Sandwich, who didn’t invent it, nor popularized it. He just liked it very much, as he could eat without leaving the card table. Hey, not every etimology’s tied to a fascinating tale, OK ?
The Bowie knife, not to be confused with David Bowie’s… sidekick… in the movie Labyrinth
Swashbuckler/buckling : from a 16th century fighting style mostly characterized by flashy moves with the sword and a small shield called buckler on the off hand. Not eponymic, but quite possibly onomatopeic : the sword “swashed” through the air and hit the buckler.
Cornelian dilemma : from French tragedy playwright Corneille, a choice one is forced to make, knowing all possible outcomes are bad for oneself, i.e. a no-win situation.
**Quixotic **: from the protagonist of the novel Don Quixote, meaning ultimately silly but well-meaning.
Along the lines of vandals, we have hooligans - from an Irish person or family (there are lots of theories but they’re all very similar) and assassins (from ‘hashishim,’ the ancient name given to an Ismaili Muslim sect).
For some of the answers that are tied to mythology, the myth might have been invented to explain the word, rather than the name of the character in the myth becoming the word. I’d bet my boots that the Greeks had the word “echo” before someone made up the story of Echo and Narcissus.
