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mid-14c., "sternness, harshness," from Old French austerite "harshness, cruelty" (14c.) and directly from Late Latin austeritatem (nominative austeritas), from austerus (see austere). Of severe self-discipline, from 1580s; hence "severe simplicity" (1875); applied during World War II to national policies limiting non-essentials as a wartime economy.