UK, 1851—a person (or persons) or a thing (or things) considered unattractive, inferior or unpleasant, compared to others of the same type or group—alludes to Cinderella’s ugly and unpleasant stepsisters in the fairy tale Cinderella
UK, 1951—‘mother-in-law’s chair’, ‘mother-in-law’s cushion’ and ‘mother-in-law’s seat’ are colloquial appellations for the globular spiny cactus Echinocactus grusonii, native to Mexico
the benefits of an endeavour are enough to outweigh the effort of pursuing it—USA, 1959—refers to the labour-intensive process of squeezing fruit to produce fresh juice
Australia, 1911—a potato farmer—composed of ‘spud’ (a potato) and ‘cocky’ (a farmer working a small-scale farm)—‘cocky’: shortened form of ‘cockatoo’ (a farmer working a small-scale farm)
the imaginary vehicle supposed to take people to the mental asylum—Australia (1869), New Zealand (1884)—the reason the colour green was chosen is unknown
also ‘like a lily on a dirt-tin’ and variants—something or somebody that is incongruous or conspicuous—UK, 1934, but chiefly Australian (from 1948 onwards)
16th century: a plant of the most familiar or frequently occurring kind, especially one that is cultivated—hence, figuratively, 19th century: something ordinary or usual for its type
‘cauliflower ear’ (USA, 1887)—French calque ‘oreille en chou-fleur’ (1913)—an ear permanently deformed as a result of injuries from repeated blows, as in boxing
the Jerusalem artichoke—UK, 1968—blend of ‘fart’ and ‘artichoke’ in ‘Jerusalem artichoke’—refers to the flatulence caused by eating Jerusalem artichokes