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assume (v.)[assume 词源字典]: early 15c., assumpten "to receive up into heaven" (especially of the Virgin Mary), also assumen "to arrogate," from Latin assumere, adsumere "to take up, take to oneself, take besides, obtain in addition," from ad- "to, up" (see ad-) + sumere "to take," from sub "under" (see sub-) + emere "to take" (see exempt (adj.)).

Meaning "to suppose, to take for granted as the basis of argument" is first recorded 1590s; that of "to take or put on (an appearance, etc.)" is from c. 1600. Related: Assumed; assuming. 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.[assume etymology, assume origin, 英语词源]
assumpsit: legal Latin, "he has taken upon himself," perfect indicative of Latin assumere (see assume).
assumption (n.): c. 1300, "the reception, uncorrupted, of the Virgin Mary into Heaven," also the Church festival (Aug. 15) commemorating this, Feast of the Assumption, from Old French assumpcion and directly from Latin assumptionem (nominative assumptio) "a taking, receiving," noun of action from past participle stem of assumere "take up, take to oneself" (see assume).

Meaning "minor premise of a syllogism" is late 14c. Meaning "appropriation of a right or possession" is mid-15c. Meaning "action of taking for oneself" is recorded from 1580s; that of "something taken for granted" is from 1620s.
assumptive (adj.): early 15c., from Latin assumptivus, from assumpt-, past participle stem of assumere "take up, take to oneself" (see assume) + -ive.
non assumpsit: "A plea in an action of assumpsit by which the defendant denies having made any promise or undertaking", Mid 17th cent.; earliest use found in Reports of Cases of the Star Chamber and High Commission. From post-classical Latin non assumpsit he did not undertake from classical Latin nōn not + assūmpsit he undertook, 3rd singular perfect indicative of assūmere.