*em-

early 15c., assumen, "arrogate, take upon oneself," from Latin assumere, adsumere "to take up, take to oneself, take besides, obtain in addition," from ad "to, toward, up to" (see ad-) + sumere "to take," from sub "under" (see sub-) + emere "to take" (from PIE root *em- "to take, distribute").

The meaning "to suppose, to take for granted without proof as the basis of argument" is recorded by 1590s; that of "to take or put on fictitiously" (an appearance, etc.) is from c. 1600. Related: Assumed; assuming.

The early past participle was assumpt. In rhetorical usage, assume expresses what the assumer postulates, often as a confessed hypothesis; presume expresses what the presumer really believes. Middle English also had assumpten "to receive up into heaven" (especially of the Virgin Mary), from the Latin past participle. The make an ass of u and me joke is attested by 1957.

late 14c., "to destroy by separating into parts which cannot be reunited, as by burning or eating," hence "destroy the substance of, annihilate," from Old French consumer "to consume" (12c.) and directly from Latin consumere "to use up, eat, waste," from assimilated form of com-, here perhaps an intensive prefix (see com-), + sumere "to take," from sub- "under" (see sub-) + emere "to buy, take" (from PIE root *em- "to take, distribute").

Specifically, "to destroy by use, wear out by applying to its natural or intended use" from c. 1400. Sense of "to engage the full attention and energy of" is from 1570s.