hypothetical subatomic particle having a fractional electric charge, 1964, applied by U.S. physicist Murray Gell-Mann (1929-2019), who said in correspondence with the editors of the OED in 1978 that he took it from a word in James Joyce's "Finnegans Wake" (1939), but also that the sound of the word was in his head before he encountered the printed form in Joyce.
German Quark "curds, rubbish" has been proposed as the ultimate inspiration [Barnhart; Gell-Mann's parents were immigrants from Austria-Hungary]; it is from Old Church Slavonic tvarogu "curds, cottage cheese" (from a suffixed form of PIE root *teue- "to swell," source also of Greek tyros "cheese"). George Zweig, Gell-Mann's co-proposer of the theory, is said to have preferred the name ace for them.