1857, "mathematical condition of being at right angles, state or fact of being normal in geometry," from normal + -cy. The word has been associated since 1920 with U.S. president Warren G. Harding (who campaigned that year under the slogan "Return to Normalcy," meaning pre-World War I conditions). Previously normalcy was used mostly in the mathematical sense and the word preferred by purists for "a normal situation" is normality. Harding's use of it was derided during his administration as an example of his much-belittled incompetence with the language (Democratic politician William G. McAdoo Jr. called Harding’s speeches "an army of pompous phrases moving across the landscape in search of an idea").
America’s present need is not heroics, but healing; not nostrums, but normalcy; not revolution, but restoration; not agitation, but adjustment; not surgery, but serenity; not the dramatic, but the dispassionate; not experiment, but equipoise; not submergence in internationality, but sustainment in triumphant nationality. [Harding, "Readjustment" speech, May 24, 1920]