a small component of a much larger structure, system or process; an insignificant individual within a large population or community—commonly associated with ‘Another Brick in the Wall’, the title of a three-part composition by the British band Pink Floyd in their 1979 rock opera ‘The Wall’, but has been used since 1867
UK, 1816—a meaningless bantering phrase—originated in a print published in June, satirising the fact that a bill on additional taxation on soap had been brought in unobtrusively in May by the Chancellor of the Exchequer
USA—‘in mothballs’ (1892): in a state or period of inactivity, disuse, reserve, storage or postponement—‘out of mothballs’ (1905): back into activity, into use
USA, 1892—a hypothetical observer of human behaviour and society whose perspective would be entirely detached and objective—fictitious prose narratives told of visits either from, or to, Mars, and had for common theme that we are far behind Mars in discoveries in the material and spiritual worlds
classical Latin ‘mare nostrum’, literally ‘our sea’: one of the names given by the Romans to the Mediterranean Sea—USA, 1824: any sea or other stretch of water belonging to, or under the control of, a nation
UK and USA, late 19th century—‘parlour socialist’: a middle- or upper-class person claiming to be committed to the cause of socialism but not actually involved in the achievement of that cause—‘parlour socialism’: the claimed commitment of a middle- or upper-class person to the cause of socialism without actual involvement in the achievement of that cause
‘parlour patriot’ (1797)—the earliest of the phrases in which ‘parlour’ is a depreciative attributive modifier used of a person claiming to be committed to a cause but not actually involved in the achievement of that cause—‘parlour’ is also used of the claimed commitment to a cause without actual involvement in the achievement of that cause
USA, 1920: ‘wetback’: an illegal immigrant who crossed the Rio Grande from Mexico to the USA—by extension: any illegal immigrant who entered a foreign country by swimming—Mexico and USA, 1994: ‘espaldas secas’, i.e., ‘dry backs’: the U.S. citizens working in Mexico as a result of the North American Free Trade Agreement