USA, 1978—to commit suicide; to demonstrate unquestioning obedience or loyalty—alludes to a mass suicide, in 1978, by members of the Peoples’ Temple in Jonestown, Guyana, who drank a cyanide-laced drink thought to be similar to Kool-Aid
Australia, 1950—a traffic warden in the state of New South Wales—‘brown’ probably refers to the colour of those traffic wardens’ uniform—‘bomber’ may refer to the fact that many of those traffic wardens were originally war veterans; or perhaps to the Australian-English use of the noun ‘bomb’ for an old car
UK, 1899—derogatory—a foreigner; a personification of foreign people—‘Johnny’ is used with modifying word to designate a person of the type, group, profession, etc., specified
military slang, 1944—a medal awarded to all members of a force—especially the 1939-1945 Star, awarded to British service personnel who took part in WWII—refers to the ubiquitousness of Spam as a foodstuff
UK, 1912—humorous: a Jewish person—refers to the Crossing of the Red Sea, as recounted in the Book of Exodus—coined on various occasions by different persons, independently from each other
USA, 1957—the rhythm method of birth control, as permitted by the Roman Catholic Church—with allusion to the unpredictable efficacy of this contraceptive method: from ‘Vatican’, denoting the authority of the Roman Catholic Church, and ‘Russian roulette’
USA, 1917—originally and chiefly military slang—an inspection of the penis for venereal disease or other infection—the image is of the penis as an additional, but shorter, limb