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femme fatale, film noir, carte blanche, cause célèbre. When the French-speaking Normans conquered England, French became the language of official institutions and practices. That happens to be the area where we find a large number of noun-adjective phrases today. Terms like attorney general, heir apparent, body politic, notary public, court martial, fee simple, and ambassador plenipotentiary all belong to the domain of officialdom. As does time immemorial, which originally referred to time “out of memory,” or before recorded time, a concept that mattered in considering whether certain customs had the force of law.
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Arika Okrent (Highly Irregular: Why Tough, Through, and Dough Don't Rhyme—And Other Oddities of the English Language)