mid-15c., "to receive up into heaven" (especially of the Virgin Mary, e.g. Feast of the Assumption, celebrated Aug. 15, attested from c.1300), from L. assumere "to take up," from ad- "to, up" + sumere "to take," from sub "under" + emere "to take" (see exempt). Early pp. was
assumpt. Meaning "to suppose" is first recorded 1590s. In rhetorical usage, assume expresses what the assumer postulates, often as a confessed hypothesis; presume expresses what the presumer really believes.