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
USA, 1918—a mechanic—since the 17th century, ‘monkey’ has been used (frequently with modifying word indicating the occupation concerned) to denote a person engaged in a trade or profession
UK, 1963—‘Mr. Plod’, also ‘P.C. Plod’, ‘Plod’: a humorous or mildly derogatory appellation for a policeman or for the police—alludes to ‘Mr. Plod’, the name of the policeman in stories by the English author of children’s fiction Enid Blyton
UK, 1989—the practice of sending food destined for the British market for irradiation in a country, typically the Netherlands, where this process is permitted, in order to mask any bacterial contamination before it is put on sale—from ‘Dutch’ and the suffix ‘-ing’, forming nouns denoting an action
UK, WWII, army slang—‘spud-bashing’ (noun): potato-peeling; ‘spud-bash’ (verb): to peel potatoes; ‘spud-basher’ (noun): one who peels potatoes—those words have also been used with reference to potato-digging
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