‘to spread [something or someone] like Marmite’ (1964)—‘like Marmite, a little goes a long way’ (1970)—Marmite is a savoury paste made from concentrated yeast and vegetable extract, used as a spread and for enriching soups and stews
the targeting of a potentially controversial message to specific voters while avoiding offending those voters with whom the message will not be popular—Canada, 1995—the image is that, like the sound made by a dog whistle, the message is only fully audible to those at whom it is directly aimed
sexual intercourse—Scotland, 1968—reduplication (with variation of the initial consonant and addition of the suffix ‘-y’) of the noun ‘rump’, denoting a person’s buttocks
a raised band across a road, designed to make motorists reduce their speed—1961—based on the image of a policeman lying asleep in the middle of a road—in early use often with reference to Jamaica
two different people or things are totally incompatible—1901—alludes to “East is East and West is West, and never the twain shall meet” in Ballad of East and West (1892), by Rudyard Kipling
a person who shows no proficiency in the use of information technology—USA, 1998—from ‘techno-’ in ‘technological’ and ‘technology’, and ‘-saur’ in ‘dinosaur’, i.e., a person who is unable to adapt to change
the Jerusalem artichoke—UK, 1968—blend of ‘fart’ and ‘artichoke’ in ‘Jerusalem artichoke’—refers to the flatulence caused by eating Jerusalem artichokes
to undertake a dangerous or hazardous operation or activity—UK, 1867, as ‘to tickle the dragon’s nose’—‘to tickle the dragon’s tail’ was used of a nuclear experiment at Los Alamos during WWII