presumption Look up presumption at Dictionary.com
early 13c., "seizure and occupation without right," also "taking upon oneself more than is warranted," from L.L. pręsumptionem "confidence, audacity," in classical L., "a taking for granted, anticipation," from pręsumere "to take beforehand," from prę "before" + sumere "to take." In English, the meaning "the taking of something for granted" is attested from c.1300. Presumptuous (mid-14c.) preserves the original sense, from O.Fr. presuntuex (12c.), from L.L. pręsumptuosus (5c.), from L. pręsumptionem.