from French plat du jour "dish of the day," which appeared from early 20c. on restaurant menus; abstracted as an all-purpose modifier by 1989. For jour "day" see journey (n.).
"short-barreled, large-caliber pistol," very effective at close range, 1850, for Henry Deringer (1786-1868), U.S. gunsmith who invented it in the 1840s. The prevailing misspelled form is how his name appeared on the many counterfeits and imitations.