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
USA, 1874—a joke made at the expense of the joke-teller’s (real or fictitious) mother-in-law; this type of joke considered (especially depreciatively) as a genre
conventionally middle-class—UK, 1953—from ‘Mrs Dale’, the name of a conventional middle-class woman in Mrs Dale’s Diary, a BBC radio serial broadcast from 1948 to 1969
looking or feeling ill or nauseated—1843, in a letter by Charles Dickens—when applied to a person, the plural noun ‘gills’ designates the flesh under the jaws and ears; also the cheeks